Question

Find the sum of all multiples of 5 upto 1017​

Answer 1

Answer

103530

Step-by-step explanation:

Sum of all multiples of 5 from 5 to 1017:

5,10,15......1015

So, a=5, d=5 and tn=1015

Now, by formula....

tn=a+(n-1)d

1015=5+(n-1)5

1015=5+5n-5

1015=5n

n=1015÷5

n=203

Now, Sn=n/2×(2a+(n-1)d)

S203= 203/2×(2×5+(203-1)5)

S203=203/2×(10+1010)

S203=203/2×(1020)

S203=203×510

S203=103530.

Sum of all multiples of 5 upto 1017 is 103530....

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