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If the average of number 148, 146, 144, 142,..... in AP be 125, then the total numbers in the series will be

A) 18
B) 24
C) 30
D) 48

Correct Answer:


B) 24

Description for Correct answer:
Given series is 148, 146, 144, 142 .....whose first term and common difference is

\( \Large a = 148,\ d = \left(146 - 148\right) = -2 \)

\( \Large S_{n}=\frac{n}{2}\left[ 2a+ \left(n-1\right)d \right] = 125 \)

=> \( \Large 125n = \frac{n}{2}\left[ 2 \times 148+ \left(n-1\right) \times \left(-2\right) \right] \)

=> \( \Large n^{2}-24n = 0 => n \left(n-24\right)=0 \)

n = 24

Part of solved Statistics questions and answers : >> Elementary Mathematics >> Statistics

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