Question

If the common different of an AP is 3, then the value of a20 - a15 =?
A) 5
B) 3
C) 15
D) 20

Answer 1

We know that,
an=a+(n-1)d
So,a20=a+(20-1)(3)
a20=a+19(3)
a20=a+57

Similarly, a15=a+14d
a15=a+14(3)
a15=a+42

Now,a20-a15=(a+57)-(a+42)
=a+57-a-42
=57-42
=15

Answer 2

Hey Mate ✌

↪ Here's your answer friend,

Given : Common difference (d) ==> 3

Let a be the first term

==> a20 = a + 19d

and

==> a15 = a + 14d

Now,

a20 - a15

==> (a + 19d) - (a + 14d)

==> a + 19d - a -14d

==> 5d

Now by substituting d = 3

we get,

5(3) = 15 is the required answer.

⭐ Hope it helps you : ) ⭐