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Ratio

by ash4gmat » Fri Dec 04, 2015 11:42 pm
Someone help solve this.

If grapes are 92% water and raisins are 20% water by weight, then how much did a quantity of raisins, which currently weighs 10 pounds, weigh when all the raisins were grapes? (Assume that the only difference between their raisin-weight and their grape-weight is water that evaporated during their transformation.)


25 pounds


46 pounds


92 pounds


100 pounds


146 pounds
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by GMATGuruNY » Sat Dec 05, 2015 3:40 am
If grapes are 92% water and raisins are 20% water, then how much did a quantity of raisins, which currently weighs 10 pounds, weigh when all the raisins were grapes? (Assume that the only difference between their raisin-weight and their grape-weight is water that evaporated during their transformation.)

A) 25 pounds

B) 46 pounds

C) 92 pounds

D) 100 pounds

E) 146 pounds
Since raisins are 20% water, the 10 pounds of raisins are composed of 2 pounds of water and 8 pounds of other stuff.
Since grapes are 92% water, the 8 pounds of other stuff must constitute 8% of the grapes:
8 = (8/100)x
x = 800/8 = 100.

The correct answer is D.
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by manik11 » Mon Dec 07, 2015 6:12 am
GMATGuruNY wrote: Since raisins are 20% water, the 10 pounds of raisins are composed of 2 pounds of water and 8 pounds of other stuff.
Since grapes are 92% water, the 8 pounds of other stuff must constitute 8% of the grapes:
8 = (8/100)x
x = 800/8 = 100.

The correct answer is D.
Mitch,
I tried to solve for the weight of raisins by equating the weight of water in both raisins and grapes. So, if raisins are 2 pound water, this 2 pound of water must constitute for 92% of grapes.
My equation looked like this:
2 = (92/100)x
x = 200/92

What am I doing wrong here?

Thanks!
Manik
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by GMATGuruNY » Mon Dec 07, 2015 6:39 am
Raisins are dried grapes: grapes that are dried in the sun so that their water content is greatly REDUCED.
Grapes contain MUCH more water than raisins do.
manik11 wrote:Mitch,
I tried to solve for the weight of raisins by equating the weight of water in both raisins and grapes. So, if raisins are 2 pound water, this 2 pound of water must constitute for 92% of grapes.
My equation looked like this:
2 = (92/100)x
x = 200/92

What am I doing wrong here?

Thanks!
Manik
The portion in red and the equation in blue misrepresent the problem.
As stated above, grapes contain much more water than raisins do.
Thus, the 2 pounds of water in the raisins must be far less than the 92% water content in the grapes.
Thus, the equation in blue is invalid.
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I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
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by manik11 » Mon Dec 07, 2015 7:07 am
GMATGuruNY wrote:Raisins are dried grapes: grapes that are dried in the sun so that their water content is greatly REDUCED.
Grapes contain MUCH more water than raisins do.
manik11 wrote:Mitch,
I tried to solve for the weight of raisins by equating the weight of water in both raisins and grapes. So, if raisins are 2 pound water, this 2 pound of water must constitute for 92% of grapes.
My equation looked like this:
2 = (92/100)x
x = 200/92

What am I doing wrong here?

Thanks!
Manik
The portion in red and the equation in blue misrepresent the problem.
As stated above, grapes contain much more water than raisins do.
Thus, the 2 pounds of water in the raisins must be far less than the 92% water content in the grapes.
Thus, the equation in blue is invalid.
Thanks a lot! Mitch...I see my mistake now.
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