Question

Find the sum of all numbers , which are divisible by 7 and lying between 50 and 500​

Answer 1

Answer:

A1 is 56 and l=427

First find (An) =54

Then sn= n/2(2a+L)

Sn=14,553

Answer 2

Answer:

17696

Step-by-step explanation:

Number range: 50 to 500

Criteria: Divisible by 7

List of numbers:

56, (56+7), 56+ (2*7) + (56+3*7) + .....+ (56 + 63*7)

Count of numbers: 64 as per above

Sum of numbers:

Since it is an AP use of respective formula:

Sn = (n/2)*(an+a1)  = 64/2*(497+ 56) = 32* 553  = 17696

So the required sum = 17696