Question

The sum of 50 + 100 + 150 + 200 + …….. + 1000 is _________

(a) 10000

(b) 14400

(c) 10500

(d) 12100

This question was addressed to me in class test.

My doubt stems from Sum of N Terms of Arithmetic Progression topic in portion Arithmetic Progressions of Mathematics – Class 10

Answer 1

Right option is (c) 10500

Easiest explanation: Here a = 50, d = 50 and Tn = 1000.

Tn = a + (n – 1)d = 1000

50 + (n – 1)50 = 1000

50 + 50n – 50 = 1000

n = 20

We know that, Sn = \(\frac {n}{2}\) (a + l)

Sn = \(\frac {20}{2}\) ((50) + 1000)

Sn = 10(50 + 1000) = 10500