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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; sixtyseven; sixtytentyfive," which is moreorless the same thing.

June 29th, 2019, 08:30 PM  #3 
Math Team Joined: May 2013 From: The Astral plane Posts: 2,257 Thanks: 928 Math Focus: Wibbly wobbly timeywimey stuff.  
June 29th, 2019, 09:17 PM  #4 
Senior Member Joined: Sep 2015 From: USA Posts: 2,530 Thanks: 1390 
60+15 = 75

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 SMJ727T1 using Tapatalk 
June 30th, 2019, 12:02 PM  #6  
Newbie Joined: Jun 2019 From: New York Posts: 23 Thanks: 0  Quote:
Sent from my SMJ727T1 using Tapatalk Last edited by skipjack; July 1st, 2019 at 04:08 PM.  
June 30th, 2019, 12:03 PM  #7 
Newbie Joined: Jun 2019 From: New York Posts: 23 Thanks: 0  
June 30th, 2019, 04:48 PM  #8 
Member Joined: Jun 2019 From: AZ, Seattle, San Diego Posts: 30 Thanks: 24  
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 ... 
June 30th, 2019, 05:24 PM  #10 
Newbie Joined: Jun 2019 From: New York Posts: 23 Thanks: 0  

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