Question

Find the sum of all the multiple s of 7 lying between 500 and 900

Answer 1

Step-by-step explanation:

Multiples of 7 from 500 to 900 are

504,511.........896

these numbers are in Arithmetic progression

so a=504 d=7

896=504+(n-1)*7

896=504+7n-7

399=7n

n=57

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

57/2[2*504+(57-1)7]

57/2[1400]

57*700

39900

Answer 2

Answer:

Step-by-step explanation: