May 6, 20214 yr Been seeing this go around the webs. 8 + 7 = 5. 4 +2 +1 = 7. For a total of 75. That there is a thread you are the undisputed champ of that already addresses this.
May 6, 20214 yr Add 8 to 7 to get the ones digit (5), then add 2+1+4 to get the tens digit (7). I don't consciously go through that process -- two digit sums just sort of appear automatically for me -- but if I break down the process that's how it happens.
May 6, 20214 yr 45 minutes ago, Laxtonto said: See 47 and 28 Subtract 3 from 28 to make 25 and add 3 to 47 to make 50 50 + 25 = 75 Add 3 to 47 to make 50, then take away 3 from 28 to make 25... Funny. Edited May 6, 20214 yr by Prepuce of Doom
May 6, 20214 yr 47 is the sixth prime number past 28, so 47 x 6 = 282 (3 digit number) since 6 = 3 x 2, 282 / 2 = 141 since 3^2 = 9, 141 + 9 = 150 150 / 2 = 75
May 6, 20214 yr Popular Post 47+20=67+8=75 I can’t be the only one who did that? And it takes less than 2 seconds. I was educated only at the finest of institutions.
May 6, 20214 yr Interesting to see how differently some of y’all broke it down to arrive at the same answer.
May 6, 20214 yr 1 hour ago, woohorn said: Is this a joke? 40+20=60 7+8=15 60+15=75 No it isn't a joke and that isn't the fastest or most accurate way of doing it if you're actually good at mental math. Even though Vic phrased the numbers in reverse. But what ChiTown said is what I do. Take the singles off the 2nd number - add the tens - then add the singles. If I'm looking at 28 + 47 I do 8 plus 47 is 55 plus 20 is 75. If I'm looking at 47 + 28 I do 47 plus 20 is 67 plus 8 is 75. YMMV. Edited May 6, 20214 yr by ztejas
May 6, 20214 yr 6 hours ago, ztejas said: No it isn't a joke and that isn't the fastest or most accurate way of doing it if you're actually good at mental math. Even though Vic phrased the numbers in reverse. But what ChiTown said is what I do. Take the singles off the 2nd number - add the tens - then add the singles. If I'm looking at 28 + 47 I do 8 plus 47 is 55 plus 20 is 75. If I'm looking at 47 + 28 I do 47 plus 20 is 67 plus 8 is 75. YMMV. Is someone timing how long each method takes? It may take someone longer to do the "fastest" method, depending on how their brain works. And how is one method more accurate than another if they all produce the correct answer 100% of the time? I personally dump 28 and 47 toothpicks on the floor and then count them all Rainman style. Edited May 6, 20214 yr by idigTexas OU sucks
May 6, 20214 yr 8 hours ago, Llogg said: 40+20+7+8 Mostly this but I pretty much see 60 + 15 even though 40+20 and 7+8 is also processing.
May 6, 20214 yr 4+2=6, see that I'm going to carry the next operation so make it a 7, then I've already done the 8+7 so tack on the 5. I didn't really know that I did that.
May 6, 20214 yr 9 hours ago, woohorn said: Is this a joke? 40+20=60 7+8=15 60+15=75 18 minutes ago, mdmost said: 7+8=15 40+20=60 15+60=75 These. And I do basic arithmetic incredibly fast and accurately in my head, using that sort of methodology. I use it in real-time, like cross-examining a witness on damages calculation, and I can usually spit out the next number before he can do it on a calculator. Nobody taught that, it's just a mental shortcut that I -- and obviously lots of other folks -- developed on their own.
May 6, 20214 yr Add the tens while peeking at the ones to see if I’ll be carrying a one. Then get the last digit from the ones 4 + 2 + (is there an extra +1? Yes. Then +1) Tens place is 7 8 + 7, last digit = 5, so ones place is 5.
May 6, 20214 yr 13 minutes ago, jeevsie said: 4+2=6, see that I'm going to carry the next operation so make it a 7, then I've already done the 8+7 so tack on the 5. I didn't really know that I did that. Ah. I see I basically wrote the same thing.
May 6, 20214 yr 19 minutes ago, Brisketexan said: These. And I do basic arithmetic incredibly fast and accurately in my head, using that sort of methodology. I use it in real-time, like cross-examining a witness on damages calculation, and I can usually spit out the next number before he can do it on a calculator. Nobody taught that, it's just a mental shortcut that I -- and obviously lots of other folks -- developed on their own. distributive property FTW
May 6, 20214 yr 10 hours ago, Vic Mackey said: Been seeing this go around the webs. 8 + 7 = 5. 4 +2 +1 = 7. For a total of 75. 20 +40 8+7 What is this horseshit you posted? PS I know a guy that can multiply 3 digit numbers by 2 numbers in his head in 3-4 seconds . It is at the same time impressive and creepy Edited May 6, 20214 yr by Dennis Taylor
May 6, 20214 yr 4+2=6, see that I'm going to carry the next operation so make it a 7, then I've already done the 8+7 so tack on the 5. I didn't really know that I did that.Same.
May 6, 20214 yr 1 hour ago, Dennis Taylor said: 20 +40 8+7 What is this horseshit you posted? PS I know a guy that can multiply 3 digit numbers by 2 numbers in his head in 3-4 seconds . It is at the same time impressive and creepy Craziest shit I’ve seen in all my years is a patient who could tell you what day of the week you were born based on birthday. And it took him less than 2 seconds. I brought in 30 different people to stump him. Impossible. Freaked me the fuck out.
May 6, 20214 yr 1 hour ago, Nolacycling said: (47 + 20) + 8 My middle school students would need a calculator. This. I wrote it out but this is the shortest, best way. Other than the memorizing guy, who is likely full of shit. Some of you make me wonder...
May 6, 20214 yr 12 hours ago, honolulu horn said: Add 8 to 7 to get the ones digit (5), then add 2+1+4 to get the tens digit (7). I don't consciously go through that process -- two digit sums just sort of appear automatically for me -- but if I break down the process that's how it happens. This is me as well.
May 6, 20214 yr 1 hour ago, Nolacycling said: (47 + 20) + 8 My middle school students would need a calculator. 16 minutes ago, Red Five said: Add 30 to 47 then subtract 2. These 2 are basically the same and pretty much both take zero time. I’m admittedly fascinated by this type of shit...
May 6, 20214 yr What happens in my brain? Where's the happens in my brain. Seriously though 7+8=15 2+4 =6(omitting the 0's) 6 +`1=7 answer 75
May 6, 20214 yr 13 hours ago, woohorn said: Is this a joke? 40+20=60 7+8=15 60+15=75 this... starting to see why "new" math teaching was developed
May 6, 20214 yr 14 hours ago, woohorn said: Is this a joke? 40+20=60 7+8=15 60+15=75 I add 4+2, then 8+7, and move the 0 to the end in my head.
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