Call 911: Some Digits are Missing

This topic has expert replies
Source: — Problem Solving |

User avatar
Master | Next Rank: 500 Posts
Posts: 435
Joined: Sat Sep 27, 2008 2:02 pm
Location: San Jose, CA
Thanked: 43 times
Followed by:1 members
GMAT Score:720

by dumb.doofus » Tue May 19, 2009 1:43 pm
I just used basic multiplication to deduce a = 5 and b = 6

so a + b = 11

any other methods??
One love, one blood, one life. You got to do what you should.
https://dreambigdreamhigh.blocked/
https://gmattoughies.blocked/

Master | Next Rank: 500 Posts
Posts: 487
Joined: Fri Mar 27, 2009 5:49 am
Thanked: 36 times

by dtweah » Wed May 20, 2009 5:26 am
dumb.doofus wrote:I just used basic multiplication to deduce a = 5 and b = 6

so a + b = 11

any other methods??
I did the same but here is what they say in the OA

Recall the tests for divisibility by 9 and by 11. Since 342 is divisible by 9, the number 100900b02 is as well. So b has to be 6. But then 100900b02 is divisible by 11. Since 342 is not divisible by 11, we deduce 29a031 must be divisible by 11. So a has to be 5, and a + b = 11.