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In Ranking Sequence questions, ranks of a person both from the top and bottom are mentioned and total number of persons is asked. However, sometimes this question is put in the form of a puzzle of interchanging seats by two persons.

In a class of 60, where girls are twice that of boys, Kamal ranked seventeenth from the top. if there are 9 girls ahead of Kamal, how many boys are after him in rank ?

Option:
A. 3
B. 7
C. 12
D. 23
E. 32
Answer: C . 12

Justification:

Let the number of boys be x.  Then, numbers of girls = 2x.
.'. x + 2x = 60  or  3x = 60  or  x = 20.
So, number of boys = 20 and numbers of girls = 40.
Number of students behind Kamal in rank = (60 - 17) = 43.
Number of girls ahead of Kamal in rank = 9.
Number of girls behind Kamal in rank = 40 - 9 = 31.
.'. Number of boys behind Kamal in rank = 43 - 31 = 12.

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