There are two examinations rooms A and B. If 10 students are sent from A to B, then the number of students in each room is the same. If 20 candidates are sent from B to A, then the number of students in A is double the number of students in B. The number of students in room A is:
Options:
A . 20
B . 80
C . 100
D . 200
E . None of these
Answer: Option C Let the number of students in rooms A and B be x and y respectively. Then, x - 10 = y + 10 ⇒ x - y = 20 . . . . . (i) and x + 20 = 2(y - 20) ⇒ x - 2y = -60 . . . . . (ii) Solving (i) and (ii) we get: x = 100, y = 80 ∴ The required answer A = 100
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