Double scoop - No of guests- Please explain on how to think

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At a certain picnic, each of the guests was served either a single scoop or a 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

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by GMATGuruNY » Wed Jan 15, 2014 11:18 am
Divya Ann Chacko wrote:At a certain picnic, each of the guests was served either a single scoop or a 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
Statement 2: Total scoops = 120
No way to determine the number of double-scoop guests.
INSUFFICIENT.

Statement 1: At the picnic, 60 percent of the guests were served a double scoop of ice cream
Thus, of every 10 guests:
6 guests received 2 scoops each, for a total of 12 scoops.
4 guests received 1 scoop each, for a total of 4 scoops.
Thus, of every 16 scoops, the fraction received by the double-scoop guests = 12/16 = 3/4.
No way to determine the number of double-scoop guests.
INSUFFICIENT.

Statement combined:
The double-scoop guests received 3/4 of the total number of scoops:
(3/4)120 = 90.
Since each of these guests received 2 scoops, the number of double-scoop guests = 90/2 = 45.
SUFFICIENT.

The correct answer is C.
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