What is the average of first 8 multiples of 4?
Explanation:
The first 8 multiples of 4 are: 4, 8, 12, ... and 32.
Sum of these numbers = 4 + 8 + 12 + ... + 32 = 4 × (1 + 2 + 3 + ... + 8) = 4 × 8 × 9/2 = 144
∴ Required average = 144/8 = 18
Alternately, The first 8 multiples of 4 are: 4, 8, 12, ... and 32.
These numbers are in Arithmetic Progression, and average of numbers is AP is same as the average of first and the last numbers.
∴ Required average = (4 + 32)/2 = 18
Hence, option (d).
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