Q. 144.5( 15 Votes )
What is the
Let the common difference be 'd' and the first term be 'a'.
And we know that, nth term of an AP is given by
an = a + (n - 1) dwhere n is the nth term
a is the first term
d is the common difference
Given: a21 - a7 = 84
a21 = a + (21 - 1) d .........eq(1)
a7 = a + (7 - 1) d .................eq(2)
Subtracting eq (2) from eq(1):
⇒ 14d = 84
⇒ d = 6
Hence, the common difference of AP is 6.
Rate this question :