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AFCAT Model Paper 7

Question : 40 of 100

Marks: +1, -0

What is the average of cubes of the first 15 odd numbers?

Solution:

Formula Used:

The sum of cubes of the first '

n

' odd numbers

=n^{2}(2 n^{2}-1)

Calculation:

We have to find the value of

1^{3}+3^{3}+5^{3}+

+29^{3}

According to the formula used

⇒

15^{2}(2 \times 15^{2}-1)

⇒ 225 × (450 – 1)

⇒ 225 × 449

Now, Required average

= \frac{225 \times 449}{15}

⇒ 6735

∴ The required average is 6735.

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