Question

find the sum of first n multiples of 5.

Answer 1

Answer:

Multiples of 5 are 5,10,15,20,25……………

S=5+10+15+20+25+30+………………n term

Here the series is an AP. in which a=5 , d=5

S=n/2.[2a+(n-1).d]

S=n/2.[2×5+(n-1)×5]

S=n/2.[10+5n-5]

S=(n/2).(5n+5)

S=5n.(n+1)/2 , answer

Answer 2

Answer:

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Explanation:

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