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### Question

Which term of this arithmetic series is zero: 81, 72, 63 ...?

**A**

10.

**B**

11.

**C**

9.

**D**

12.

**Soln.**

**Ans: a**

The first term is 81, common difference is d = -9, n-th term is 0. So $0 = 81 + (n - 1) × -9$ which gives $n = 1 + {81/9} = 10$.