Question

find the sum of all natural number between 1 to 1000 that are multiple of 5​

Answer 1

Step-by-step explanation:

multiple of 5 means the A. P is

5,10,15.......995,1000

first term =5

and last term is = 1000

common difference=5

sum of all natural number =Sn

first of all we have to find n

tn = a+(n-1)d

1000=5+(n-1)5

1000=5+5n-5

1000=5n

n=1000/5

n=200

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

Sn=200/2[2×5+(200-1)5]

Sn=200/2[10+199×5]

Sn=200[5+995]

Sn=200×1000

Sn=200000