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If the mean of the observations 2, 5, 7, a, 11, b is 7, and it is also known that a = b + 3, find the value of a.

Class 9Measures of Central TendencyStatistics and Probability

A9
B20
C10
D11

Step-by-Step Solution

Sum =

2 + 5 + 7 + a + 11 + b = 25 + a + b

. Mean over 6 = 7, so

25 + a + b = 42

, giving

a + b = 17

. With

a = b + 3 : (b + 3) + b = 17, 2 b = 14, b = 7, a = 10

.

Answer: C) 10

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