Question

If $A=\{1,3,5,7\}$ and $B=\{1,2,3,4,5,6,7,8\}$, then the number of one-to-one functions from $A$ into $B$ is

• A. 1860
• B. 1880
• C. 1430
• D. 1680

Answer 1

Answer: (D)

Number of one-one functions from A to B
${=}^n{C}_m\times m!,$ Where n $\ge$ m
$={}^8{C}_4\times 4!=1680$