Question

find the sum of first 20 multiples of 8

Answer 1

ap=8,16,24,......,160.

here,a=8

d=8

l=160

so,sn=n/2(a+l)

=20/2(8+160)

=10×168

=1680...

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Answer 2

Given : First 20 multiples of 8

To find : Their sum.

Solution :

We can simply solve this mathematical problem by using the following mathematical process. (our goal is to calculate the sum of the first 20 multiples of 8)

The series of multiples of 8 is = 8,16,24...

Number of multiples = 20

So, instead of manual calculations, we can apply AP series formula.

In this case,

• First term of AP (a) = 8
• Common difference (d) = Second term - First term = 16 - 8 = 8
• Number of terms (n) = 20

Now, we know that,

Sum of n terms of an AP series = (n/2) × [2a + (n-1) × d]

By, putting the available data, in the above mentioned mathematical formula, we get :

Sum of first 20 multiples = (20/2) × [(2 × 8) + (20 - 1) × 8] = 10 × (16 + 152) = 1680

(This will be considered as the final result.)

Hence, the sum of first 20 multiples of 8 is 1680