Question

find sum of 5,15,25,35,.......,995​

Answer 1

Answer:

Sn = n/2(a+l)

where n = no of terms, a = first no

and l = last number.

then an = a+(n-1)d

then (n-1)= 995-5/10 = 99

then n = 99+1 = 100

then putting in 1st formula...

Sn = 100/2(5+995) = 50×1000 = 50000 answer.....

hope it helps.....

thanks

Answer 2

Answer:

L = 995

a + (n - 1)d = 995

5 + (n -1)10 = 995

5 + 10n -10 = 995

10n - 5 = 995

10n = 1000

n = 1000/10 = 100

Total sum = n/2 (a + L)

= 100/2(5 + 995)

=. 50 × 1000

= 50000. Ans...