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Ratio (Ice Cream Scoops)

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Ratio (Ice Cream Scoops)

by EMAN » Mon Oct 12, 2009 10:03 am
At a certain picnic, each of the guests was served either a single scoop or double scoop of ice cream. How many of the guests were served a double scoop of ice cream?

(1) At the picnic, 60 percent of the guests were served a double scoop of ice cream.

(2) A total of 120 scoops of ice cream were served to all the guests at the picnic.




Using all this information, how would you actually solve this question mathematically.
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Source: — Data Sufficiency |
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by mp2437 » Mon Oct 12, 2009 11:13 am
Answer: C

Let d = double, s = single

(1) d/(d + s) = 0.60 --insufficient by itself
(2) s + 2d = 120 --insufficient by itself

(1) + (2):

using (2): s = 120 - 2d, plug it into (1) -

d/(d+s) = 0.60 --> d/(d + 120 - 2d) = 0.60
d/(120-d) = .6 --> solving gives d = 45.

Plug into any equation, get s = 30.

Choice C.
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