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sunilrawat: Master | Next Rank: 500 Posts; Posts: 112; Joined: Sun Jun 13, 2010 9:20 am; Thanked: 5 times; GMAT Score:640

by sunilrawat » Sat Jun 11, 2011 4:28 am

a rainstorm increased the amount of water from 124 bn gallons to 138 bn gallons. If storm increased the amount of water to 82% of the total capacity, approx how many bn gallons of water was the reservoir short of the total capacity prior to the storm.

a 9
b 14
c 25
d 30
e 44

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Source: Beat The GMAT — Problem Solving | Sat Jun 11, 2011 4:28 am

Frankenstein: Legendary Member; Posts: 1448; Joined: Tue May 17, 2011 9:55 amFollowed by: 53 members; Location: India; Thanked: 375 times

by Frankenstein » Sat Jun 11, 2011 4:41 am

Hi,
Let V be the total capacity of reservoir.
138 bn gallons is 82% of total capacity of reservoir.
So, (0.82)V = 138 => V =~ 168.
Initially volume of water is 124.
So, unfilled volume of reservoir is 168-124 = 44 bn gallons

Hence, E

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manpsingh87: Master | Next Rank: 500 Posts; Posts: 436; Joined: Tue Feb 08, 2011 3:07 amFollowed by: 6 members; Thanked: 72 times

by manpsingh87 » Sat Jun 11, 2011 4:43 am

sunilrawat wrote:a rainstorm increased the amount of water from 124 bn gallons to 138 bn gallons. If storm increased the amount of water to 82% of the total capacity, approx how many bn gallons of water was the reservoir short of the total capacity prior to the storm.

a 9
b 14
c 25
d 30
e 44

let the capacity of reservoir be x. Therefore,
138=82%of x;
x=168 approx.
so before storm reservoir was 168-124=44 bn gallons of water short of its capacity.

hence E

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sunilrawat: Master | Next Rank: 500 Posts; Posts: 112; Joined: Sun Jun 13, 2010 9:20 am; Thanked: 5 times; GMAT Score:640

by sunilrawat » Sat Jun 11, 2011 4:55 am

i solved it like this,

if 124 if x% of capacity (V)

0.82V = 138
0.01xV = 124

solving, we get x ~ 73%, i.e 27% short of V

then instead of calculating 27%of V, I marked 25 as the option...silly mistake

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cans: Legendary Member; Posts: 1309; Joined: Mon Apr 04, 2011 5:34 amFollowed by: 123 members; Location: India; Thanked: 310 times; GMAT Score:750

by cans » Tue Jun 14, 2011 3:28 am

82% of total=138
total=138*100/82 = 6900/41 = 168. something
thus remaining when 124 was filled = 168-124 = 44
IMO E

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