Question

Which term of the A.P 21,42,63,84.......is 210​

Answer 1

T₁₀

Explanation:

We know the first term is 21, which is a

We work out the difference by taking 21 away from 42 which equals 21.

We then use the general formula:

Tₓ = a + (x-1)(d)

We need to find the term which equals 210

210 = 21 + (x - 1)(21)

210 = 21 - 21 + 21x

210 = 21x

x = 10

Hence it is the 10 term when the thing equals 210.