What is the units digit of (23)^7 * (12)^8 * (517)^22 ?

Question

(A) 9 
(B) 5 
(C) 8 
(D) 1
(E) 3

gmatophobia · Answer

Cyclicity of 3 =  3 \quad 9 \quad 7 \quad 1  
 Cyclicity of 2 =  2 \quad 4 \quad 8 \quad 6  
 Cyclicity of 7 =  7 \quad 9 \quad 3 \quad 1

Unit Digit of  (23)^7  = 7  
 Unit Digit of  (12)^{8}  = 6 
 Unit Digit of  (517)^{22}  = 9

Units digit of  (23)^7 * (12)^8 * (517)^{22} = 7 * 6 * 9 = 42 * 9  = XX 8

Option C

Prep Toolkit