Assessment Exam Category

A Students was asked to find the arithmetic mean of the numbers 3, 11, 7, 9, 15, 13, 8, 19, 17,
21, 14 and x. He found the mean to be 12. What should be the number in place of x?
a) 3 b) 7 c) 17
d) 31 e) None of these

Read Solution (Total 1)

The arithmetic mean of the numbers is= (3 + 11 + 7 + 9 + 15 + 13 + 8 + 19 + 17 + 21 + 14 + X) / 12
= (137+X)/12

According to the question,
(137+X)/12=12
or, 137 + X = 12x12
or, 137+ X = 144
or, X= 144 - 137 = 7

So, the number in place of X should be 7.
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Assessment Other Question

The cost of carpeting a room 18 m long with a carpet 75 cm wide at Rs.4.50 per metre is Rs.810.
The breadth of the room is :
a) 7 m b) 7.5 m c) 8 m
d) 8.5 m e) None of these Which of the following is a pair of co-primes?
a) (16, 62) b) (18, 25) c) (21, 35)
d) (23, 92) e) None of these