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 June 29th, 2019, 05:11 PM #1 Newbie   Joined: Jun 2019 From: New York Posts: 23 Thanks: 0 Math Challenge How do you add up 27 and 48 in your head? My method 20 + 40=60, 60 +7=67, 67+8=75. What is your method?
 June 29th, 2019, 06:34 PM #2 Senior Member   Joined: Jun 2019 From: USA Posts: 124 Thanks: 41 For me, it goes, "sixty; sixty-seven; sixty-tenty-five," which is more-or-less the same thing. Thanks from topsquark and NinjaX3
June 29th, 2019, 08:30 PM   #3
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Quote:
 Originally Posted by NinjaX3 How do you add up 27 and 48 in your head? My method 20 + 40=60, 60 +7=67, 67+8=75. What is your method?
An abacus.

-Dan

 June 29th, 2019, 09:17 PM #4 Senior Member     Joined: Sep 2015 From: USA Posts: 2,530 Thanks: 1390 60+15 = 75 Thanks from NinjaX3 and Otis
 June 30th, 2019, 12:00 PM #5 Newbie   Joined: Jun 2019 From: New York Posts: 23 Thanks: 0 Cool! that's how you solve that problem in your mind. Sent from my SM-J727T1 using Tapatalk
June 30th, 2019, 12:02 PM   #6
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Quote:
 Originally Posted by DarnItJimImAnEngineer For me, it goes, "sixty; sixty-seven; sixty-tenty-five," which is more-or-less the same thing.
That is interesting, how you came up with that. I hadn't thought of it that way. Brilliant!

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Last edited by skipjack; July 1st, 2019 at 04:08 PM.

June 30th, 2019, 12:03 PM   #7
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Quote:
 Originally Posted by topsquark An abacus. -Dan
You could use that interesting.

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June 30th, 2019, 04:48 PM   #8
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Quote:
 Originally Posted by topsquark An abacus.

 June 30th, 2019, 05:14 PM #9 Math Team     Joined: Jul 2011 From: Texas Posts: 3,002 Thanks: 1587 $27+48 = 3 \cdot 9+3 \cdot 16 = 3(9+16) = 3(25) = 75$ it's how Ramanujan would do it ... Thanks from NinjaX3
June 30th, 2019, 05:24 PM   #10
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Quote:
 Originally Posted by skeeter $27+48 = 3 \cdot 9+3 \cdot 16 = 3(9+16) = 3(25) = 75$ it's how Ramanujan would do it ...
Excellent, That is another way of doing it.

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