Question

Which term of following A.P. is −940.

50, 40, 30, 20 ........

Activity :- Here a = `square`, d = `square`, t_n = −940

According to formula, t_n = a + (n − 1)d

−940 = `square`

n = `square`

Answer 1

Here a = 50, d = 40 − 50 = −10, t_n = −940

According to formula, t_n = a + (n − 1)d

−940 = 50 + (n − 1)(−10)

∴ – 940 = 50 – 10n + 10

∴ – 940 = 60 – 10n

∴ 10n = 60 + 940

∴ 10n = 1000

∴ n = `1000/10`

n = 100