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ds:numbers

by arjunshn » Fri Apr 22, 2011 12:52 am
On Christmas, a class teacher gave a gift pack to each student present in a class. Each pack had x chocolates,y biscuits and z toffes. How many students were there in the class?
(1) Each student received chocolates, biscuits and toffees in the ratio 1:2:4.
(2) The class teacher distributed a total of 7 chocolates, 14 biscuits and 28 toffees and the number of students present in the class was more than 1.
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Source: — Data Sufficiency |
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by force5 » Fri Apr 22, 2011 1:59 am
B

no of students will be a whole number.

(1) this ratio can be obtained by any value of students
(2) true since each had same number of chocolates he could have either given all 7 to one student or 1 each to 7 students. to remove this ambiguity statement 1 says students present in class are more than 1 hence there were 7 students.
Hence B
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by jaymw » Fri Apr 22, 2011 3:07 am
B

no of students will be a whole number.

(1) this ratio can be obtained by any value of students
(2) true since each had same number of chocolates he could have either given all 7 to one student or 1 each to 7 students. to remove this ambiguity statement 1 says students present in class are more than 1 hence there were 7 students.
Hence B
Exactly! It might also help to have a look at the prime factorization of the numbers given in B.

7 = 7
14 = 2*7
28 = 2*2*7

The only prime factors that all of these three integers have in common is 7. Since we already know that there is more than 1 student in the class, the answer must be 7.
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