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# averages

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Manager
Joined: 08 Jan 2003
Posts: 132
Location: Ukraine
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averages [#permalink]  29 Sep 2003, 08:53
Guys, a simple problem, but..:
After 5 games, a rugby team had an average of 28 points per game. In order to increase the average by n points, how many points must be scored in a 6th game?
(A) n
(B) 6n
(C) 28n
(D) 28 + n
(E) 28 + 6n

Each time I plug the numbers I get different results. Can't figure out what the problem is...

If n=2, then 5x28=140; 6x30=180; 180-140=40;
If n= 4, then ..............; 6x32=192; 192-140=52;
None of the answers above. where's the error?
Manager
Joined: 26 Aug 2003
Posts: 233
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To increase the points by a certain number n, you must score at least as many as the previous average PLUS total number of games times n.

If n = 2, your desired average is 30. Thus:
5 * 28 = 140 (so far)
(6 * 30) = 180 (desired)

180 - 140 = 40 (this is the difference between desired and current)

Now, here is the part you missed
40 - 28 = 12
subtract the minimum points you need to keep at the current average, because you're looking for the EXTRA points (or n) in every game to bring up the overall average.

Sanity check... n = 12 / 6 = 2. Works!
Manager
Joined: 08 Jan 2003
Posts: 132
Location: Ukraine
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wonder_gmat:
Thanks a lot. I am clear now.
CEO
Joined: 15 Aug 2003
Posts: 3469
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vaka wrote:
wonder_gmat:
Thanks a lot. I am clear now.

1. The sum is 140 for 5 games

2. In the sixth game,let the points scored be x ...we want the average to increase by n points..so it follows that..

(140 + x)/6 = 28+n

140+x = 168+6n

x =28+6n

thanks
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