Sum

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`

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#### Solution

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**

Concept: Arithmetic Progression

Is there an error in this question or solution?

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