Question

In the group $\{1,2,3,4,5,6\}$ under multiplication modulo $7,2^{-1}\times 4$

• A. 1
• B. 4
• C. 2
• D. 3

Answer 1

Answer: (C)

Here 1 is i.d. . eff
Since $2\times 4=8=1$ (mod 7 ) $\therefore 2^{-1}=4$
$\therefore 2^{-1}\times 4=4\times 4=2$ (mod 7)