I think this has been solved before in this forum but cant find the link.
Her's how u can solve it using the rows(I think the column approach is alittle easier than this one but I tend to use rows than columns so here it goes)
If you notice the sum of first row is 28
Second row = 2 times the first row and all negative = -2(28) = -56
Third row = 3 times first row but and all positive = 3 (28)
Fourth row = 4 times the first row but all negative = -4(28)
Similarly we can do it for other rows...
If you add all 7 rows u get
1(28)-2(28)+3(28)-4(28)+5(28)-6(28)+7(28)
= 28 * (1-2+3-4+5-6+7)
= 28 * 4
= 112
PS question....
This topic has expert replies
Source: Beat The GMAT — Problem Solving |
-
cramya
- Legendary Member
- Posts: 2467
- Joined: Thu Aug 28, 2008 6:14 pm
- Thanked: 331 times
- Followed by:11 members
think this has been solved before in this forum but cant find the link.
Here's how u can solve it using the rows(I think the column approach is a little easier than this one but I tend to use rows than columns so here it goes)
If you notice the sum of first row is 28
Second row = 2 times the first row and all negative = -2 ( 28 ) = -56
Third row = 3 times first row but and all positive = 3 ( 28 ) = 84
Fourth row = 4 times the first row but all negative = -4( 28 ) = -112
Similarly we can do it for other rows...
If you add all 7 rows u get
1( 28 ) - 2( 28 ) +3( 28 ) -4( 28 ) +5( 28 ) -6( 28 ) +7( 28 )
= 28 * (1-2+3-4+5-6+7)
= 28 * 4
= 112
Here's how u can solve it using the rows(I think the column approach is a little easier than this one but I tend to use rows than columns so here it goes)
If you notice the sum of first row is 28
Second row = 2 times the first row and all negative = -2 ( 28 ) = -56
Third row = 3 times first row but and all positive = 3 ( 28 ) = 84
Fourth row = 4 times the first row but all negative = -4( 28 ) = -112
Similarly we can do it for other rows...
If you add all 7 rows u get
1( 28 ) - 2( 28 ) +3( 28 ) -4( 28 ) +5( 28 ) -6( 28 ) +7( 28 )
= 28 * (1-2+3-4+5-6+7)
= 28 * 4
= 112
How do you solve it the Column way?cramya wrote:think this has been solved before in this forum but cant find the link.
Here's how u can solve it using the rows(I think the column approach is a little easier than this one but I tend to use rows than columns so here it goes)
-
Morgoth
- Master | Next Rank: 500 Posts
- Posts: 316
- Joined: Mon Sep 22, 2008 12:04 am
- Thanked: 36 times
- Followed by:1 members
One more way:
You can easily identify the pattern here:
First Column = 1 -2 + 3 - 4 + 5 - 6 + 7 = 4
Second Column = 2 - 4 + 6 - 8 + 10 - 12 + 15 = 8
The middle row is just the median of all values
sum the middle row = 4 + 8 + 12 + 16 + 20 + 24 + 28 = 112.
Hope this helps.
You can easily identify the pattern here:
First Column = 1 -2 + 3 - 4 + 5 - 6 + 7 = 4
Second Column = 2 - 4 + 6 - 8 + 10 - 12 + 15 = 8
The middle row is just the median of all values
sum the middle row = 4 + 8 + 12 + 16 + 20 + 24 + 28 = 112.
Hope this helps.
