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2 days to go..pls help

by rdchandvadkar » Mon Feb 15, 2010 12:31 pm
Hey, i need help.. how to solve this one:

141) The cost of a square slab of concrete is proportional to the thickness and also proportional to the square of the length. What is the cost of square slab that is 3 meters long and 0.1 meters thick?
a. 2m long by 0.2m thick is $160 more than 2m long by 0.1m thick
b. 3m long by 0.1m thick is $200 more than 2m long by 0.1m thick


Answer: D
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Source: — Data Sufficiency |
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by ajith » Mon Feb 15, 2010 12:48 pm
rdchandvadkar wrote:Hey, i need help.. how to solve this one:

141) The cost of a square slab of concrete is proportional to the thickness and also proportional to the square of the length. What is the cost of square slab that is 3 meters long and 0.1 meters thick?
a. 2m long by 0.2m thick is $160 more than 2m long by 0.1m thick
b. 3m long by 0.1m thick is $200 more than 2m long by 0.1m thick


Answer: D
The cost of a square slab = a constamt, k* thickness,t *square of the length,l^2

c = ktl^2

1.) k*0.2*4- k*0.1*4 =160 => 0.4 k =160 k =400
the cost of square slab that is 3 meters long and 0.1 meters thick = ktl^2 = 400*0.1*9 = 360 Dollars

Sufficient

2) k*0.1*9 - k*0.1*4 = 200 => 0.5k = 200 k =400
the cost of square slab that is 3 meters long and 0.1 meters thick = ktl^2 = 400*0.1*9 = 360 Dollars

Sufficient

Hence D
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