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Howie Hua @howiehua.bsky.social

Jul 8, 01:27 AM

It's Mental Math Monday! How would you mentally calculate 47+48?

🎤 Whisper Transcript (en) ⏱ 12s

"For today's Mental Math Monday, what's the first method that comes to mind when you have to calculate 47 plus 48? Think about it, and please share how you would do it in the comments."

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Howie Hua @howiehua.bsky.social · Jul 6, 11:34 AM

It's Mental Math Monday! How would you mentally calculate 47+48?

<div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:yj2k7gp2i2raray53vaanxia/bafkreicbvvjm6lstxdhtdr4q3piuz37vuf44vgmodkivkcixta2sl77odm" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Sam Taggart</span> <span class="text-[10px] text-slate-500">@sasworkshops.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 01:02 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">40+40=80 7+8=15 80+15=95 Unsure if that is the easiest way but it works for me</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:tg4ok5ate5mkmj46lecqtert/bafkreiafoyklaybaa6524uov7co6pukhunidlxpysdg35wgqrky24vl4fq" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Jim Simons</span> <span class="text-[10px] text-slate-500">@pippinsboss.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 12:51 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">Having played a lot of table tennis in my youth, number bonds ro 15 jump out at me, so 80+15</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:t5tyrordxc6srsxvfxajrakv/bafkreiea3ihi5qnsplzmhj4cpocjqckbnkvilltiqgy4f4chsb3dzpkyze" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Michael Wilkinson</span> <span class="text-[10px] text-slate-500">@mwmathsci.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 11:57 AM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">50+50-5</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:t3idpjmpvaf3pfxyl3kuuidk/bafkreihi3xshpmnyo2rosqnv3zjq2j72quipahrw6oljiuaeletxs4ipde" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">The OG Aloof Wife</span> <span class="text-[10px] text-slate-500">@nancywilkening.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 11:48 AM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">80 90 95</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:rijysdzjfdxdjgbjl5222l3c/bafkreie6kdz65as4ztgvromfhcuggrxi2ruyyo4777r4v6cttslnwzkpgm" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">JB</span> <span class="text-[10px] text-slate-500">@eljhonb.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 11:49 AM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">50+47-2</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:qxod4na55momtcr652glq4c6/bafkreib5tguwqaikfgxxquzx24qobypqwyff3bifye5uyjo25aa3v3ofs4" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">ryandougherty.bsky.social</span> <span class="text-[10px] text-slate-500">@ryandougherty.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 12:34 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">I made both number 50 (by adding 3 to 47 and 2 to 48.) 50 + 50 = 100 I then subtracted the 5 that I added and got an answer of 95. 100 – 5 = 95</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:q5qi7uhk3ua52vdmiscyugdf/bafkreibc3hugudm6lyv55h6hpk5demjynzddkpp22i733cakwjwp5dh7fa" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Karen Campe</span> <span class="text-[10px] text-slate-500">@karencampe.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 02:36 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">47 + 48 40 + 7 + 40 + 8 80 + 15 95</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:pedjbltvax3dmg3i46sceyv6/bafkreibkse2fvnsrtb6zzjaed2s63wukv26eh43m2jqbfspkkyplt554qm" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Lucky Earther</span> <span class="text-[10px] text-slate-500">@reedjam.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 12:14 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">50+50 -3-2</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:oz4wa4ksu5xz2sxo6n64vw4q/bafkreiaohogdxajyn5f65wd5tdqgw4lggiqzxexgmcwvoqvn33p5s6edr4" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Gerd Duerner</span> <span class="text-[10px] text-slate-500">@gerdduerner.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 01:59 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">My mind went: &quot;That's 5 short of hundred&quot; seeing those numbers.</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:nphfovpb4fvemofru4bv3jrt/bafkreiaw27cknph5auxu4do6nfg6umqyyolsg3h5vxujimlv5suttn5eaq" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Maëlle Fouquenet</span> <span class="text-[10px] text-slate-500">@fouquenet.eurosky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 11:45 AM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">50+50-3-2</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:ldtp27gqevzf5oan4rykhlso/bafkreiehjzd4kykw37acoh2lrj42hbi7hhbw5wsd5zg5fyt6dq7bd6vupy" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Peter Newbury</span> <span class="text-[10px] text-slate-500">@polarisdotca.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 05:30 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">Many hours of my childhood spent playing cribbage with my granny: 8 and 7 jump out as 15. Then two 40’s for a total of 95.</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:l5yz32nydpebjlcdfgycmf3x/bafkreibbgv5tn3imq5rzxlfmx32u7vranlmgc3qbfhg5gsryg7fn23ork4" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Ted Han★ 韓聖安</span> <span class="text-[10px] text-slate-500">@knowtheory.net</span> <span class="text-[9px] text-slate-600">· Jul 6, 11:39 AM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">40+40+15 is where I immediately jump to.</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:kxpg6jybriferhoeqzxhp6mb/bafkreihs7fvom34vymhsnflrurrjln7nx3uhr2g4xnnegh2u4bdbknfxpe" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">David Gutiérrez</span> <span class="text-[10px] text-slate-500">@davidcalculin.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 11:55 AM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">Mix of estimation and calculus: I know 47+48 is 90+something 7+8=15, ends in 5 So 95</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:klnt5gnyd42vus3app2k3f5i/bafkreie5d2uicjcqpodtu5v4czb6sw3yvcg6eyhsbpkhcednz52wsiafli" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Wrycke</span> <span class="text-[10px] text-slate-500">@wrycke.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 01:33 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">Not sure I can be helpful on this one - I look at it and immediately go &quot;95,&quot; like reading an extremely familiar word</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:jlgcoealqhxepv5fjp7caxlm/bafkreiebxbxdc566rgarpeb2oitof5yzu5uplic57pofsdysjv4bgj3nwi" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Carl</span> <span class="text-[10px] text-slate-500">@mathowitz.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 01:37 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">This feels more complicated than just adding, but it's what my brain did... I know that if the average of n numbers is x, then their sum is n*x. On inspection I know the average is 47.5 and somehow I knew 47.5*2=95</p> </div> </div>  <div class="mt-2"> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:jlgcoealqhxepv5fjp7caxlm/bafkreiebxbxdc566rgarpeb2oitof5yzu5uplic57pofsdysjv4bgj3nwi" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Carl</span> <span class="text-[10px] text-slate-500">@mathowitz.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 09:16 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">I asked my 10yo &amp;quot;i would do 40+40=80 plus 7+8=15, so 95. You would probably do 50+50 minus 2 and 3&amp;quot;</p> </div> </div>  </div> </div> </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:iclp5btanewlnkkjckdu6sqg/bafkreia5g6pt2ab5f4zx5r2mhb7pk3l5opk54cmqmuw2obmdwjjofo7y7q" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Jamie Wood</span> <span class="text-[10px] text-slate-500">@jamiewoodmaths.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 02:35 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">Add the 2 from 47 to 48 to get 50. Then add 45 95</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:h22inlt4hakcgm6xqkbzl5s3/bafkreib7osd4jig5l53err22joddlhaq6mdlayrdz4ikmzlnohqxwp4pny" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">katehelwig.bsky.social</span> <span class="text-[10px] text-slate-500">@katehelwig.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 12:14 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">100-5!</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:glhbfaip6o54nax5my5dgpck/bafkreibgivi7r4rz6e5ot64w2qpama6fuj7tpo2bybzk4qhcyuzdvdmrkm" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Mark Pekala</span> <span class="text-[10px] text-slate-500">@markpekala.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 12:03 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">80 + 15 = 95</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:gb32y6grgwohfxqlcyver2a7/bafkreigtvaj3ecubw75cwmnvgdra4peknldfqdvrptsb2fmdrydi7yytwq" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">W. Ethan Duckworth</span> <span class="text-[10px] text-slate-500">@weduckworth.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 12:58 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">2*47+1 = 95</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:c72rtptyi5xnrjw4eni22qr4/bafkreibuitlveelbuhr5q6qc6pddbt5phfmlyzkejb5dbz7qptrkasytuy" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">Paddy MacMahon</span> <span class="text-[10px] text-slate-500">@paddymacmahon.com</span> <span class="text-[9px] text-slate-600">· Jul 6, 12:36 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">Hard to describe. I looked at it and said 95. I *think* my process is probably recognising that two numbers in the late forties add to ninety-something; the 8 and 7 mean the something must be 5.</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:7xtl7gu32m2xwmv3crlvweg5/bafkreigelfldm6heyhnec4rmq4ont6x74krzluvcwwlh3vdwesyrofj24q" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">grndkntrl</span> <span class="text-[10px] text-slate-500">@grndkntrl.eurosky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 12:28 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">45+45+2+3</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:56xccnqq43dtf2zba3rcmwzr/bafkreihkri22k4za3d4cmyxe2chw4dnqboz5v2vefrrvjn6p6caca544d4" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">A Teacher Type Resources</span> <span class="text-[10px] text-slate-500">@ateachertype.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 12:42 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">Abacus brain here. Units: 7+3 for 10; -&gt; 5 as the units. Tens: (40+10)+40; -&gt; 90 as the tens. 95.</p> </div> </div>  </div> <div class="border-l-2 border-slate-800/60 pl-4 py-2 mt-3 ml-2"> <div class="flex items-start gap-2.5">  <img src="https://cdn.bsky.app/img/avatar/plain/did:plc:56f3c2pxqfjwiahlfqr2ls6m/bafkreibiupqtgp5ibrxypqhxieaaqbo6nt2l5xwluuvgmgd32c7ysoonku" class="w-6 h-6 rounded-full shrink-0 border border-slate-800" />  <div class="flex-1 min-w-0"> <div class="flex items-center gap-2 mb-1"> <span class="text-xs font-bold text-slate-300">AmyL0317</span> <span class="text-[10px] text-slate-500">@amyk1025.bsky.social</span> <span class="text-[9px] text-slate-600">· Jul 6, 01:24 PM</span> </div> <p class="text-xs text-slate-350 leading-relaxed break-words">45 + 45 is 90, then 2 + 3. 90 + 5 is 95</p> </div> </div>  </div>

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