Question

If for AP, T25-T20=15 then d=__
Options : 1) 3
2) 5
3) 20
4) 25
(step by step explanation only) ​

Answer 1

Answer:

Tn= t+(n-)d where

t= first term

d=common difference

n= number of terms

T25= t+(25-1)d

= t+24d. . . . . . (1)

T20=t+(20-1)d

= t+19d. . . . . . . (2)

According to the question

T25-T20=15

From equation (1) and (2) we get

t+24d - (t+19d)=15

t+24d-t-19d=15

24d-19d=15

5d=15

d=3

Option (1) is the correct answer