Question

7+21/2+14+........+84 , find sum

Answer 1

Answer:

use A.P.

where a is first term d is common difference and TN is number of terms

therefore here a=7 i.e.14/2

d=7/2 TN =84

An=n/2(2a +(n-1)d)

2*14/2+84-1*7/2

therefore 84/2(14+83*7/2)

42(14+83*7/2)

therefore 42/2=21

21(14+83*7)

21(14+581)

21(595)

12495 is the answer