SECTION – 1

20. The unit digit in the product of (8267)¹⁵³ x (341)⁷² is

A. 1 B. 2 C. 7 D. 9

Solution:

(8267)¹⁵³ has a units digit which is that of 7¹⁵³ and 341⁷² has a units digit which is that of 1⁷²

7¹⁵³ = 7^{4(38) +1} ––– (1)

The units digits of successive powers of 7 are 7,9,3,1;7,9,3,1 etc

(1) Þ units digit of 7¹⁵³ = that of 7¹ = 7.

The units digits of 1⁷² = 1.

∴The required units digit = 7 (1) = 7. Choice (C)