Question

Write an algebraic expression for the given series.

12, 23, 34, 45, ......

• A. 10n + 2
• B. 11n + 1
• C. 12n - 1
• D. 11n - 1

Answer 1

The correct option is B

11n + 1

Let n be a variable that denotes natural numbers (1, 2, 3, 4...).

Observe the numbers.

12 = 11 + 1 = 11 x 1 + 1; n = 1
23 = 22 + 1 = 11 x 2 + 1; n = 2
34 = 33 + 1 = 11 x 3 + 1; n = 3
45 = 44 +1 = 11 x 4 + 1; n = 4

All these numbers are obtained by multiplying natural numbers (n) with 11 and adding 1 to the resulting product.

Therefore the algebraic expression for the given series is
11n + 1, where n = 1, 2, 3, ... in order.