Question

Sol. (4) Expression ( =(2137)^{754} ) Unit's digit in ( 2137=7 ) Now, ( 7^{1}=7,7^{2}=49,7^{3}=343,7^{4}=2401 )
( 7^{5}=16807, ldots ldots ldots . ) Clearly, after index ( 4, ) the unit's digit follow the same order. Dividing index 754 by 4 we get remainder ( =2 )
( therefore ) Unit's digit in the expansion of ( (2137)^{754}= ) Unit's digit in the expansion of ( (2137)^{2}=9 )

# Ex.3. The unit's digit in the expansion of (2137)754 is (1) 1 (2) 3 (4) 9 (3) 7

Solution