Question

Find the sum of the following APs.

(i) 2, 7, 12 ,…., to 10 terms.

(ii) − 37, − 33, − 29 ,…, to 12 terms

(iii) 0.6, 1.7, 2.8 ,…….., to 100 terms

(iv) ,………, to 11 terms

Answer 1

(i)2, 7, 12 ,…, to 10 terms

For this A.P.,

a = 2

d = a₂ − a₁ = 7 − 2 = 5

n = 10

We know that,

(ii)−37, −33, −29 ,…, to 12 terms

For this A.P.,

a = −37

d = a₂ − a₁ = (−33) − (−37)

= − 33 + 37 = 4

n = 12

We know that,

(iii) 0.6, 1.7, 2.8 ,…, to 100 terms

For this A.P.,

a = 0.6

d = a₂ − a₁ = 1.7 − 0.6 = 1.1

n = 100

We know that,

(iv). …….. , to 11 terms

For this A.P.,

n = 11

We know that,