Question

What is the common difference of an AP in which a₂₇ – a₇ = 84?

Answer 1

Given: a₂₇ – a₇ = 84. Use nth term formula a_n = a + (n – 1)d.

a₂₇ – a₇ = [a + 26d] – [a + 6d]

= 26d – 6d

= 20d

So, 20d = 84

⇒ `d = 84/20` 

= `21/5`

= 4.2

The common difference d = `21/5` or 4.2.