Question

The number of ways of selecting a boy and a girl from a class consisting of $20$ boys and $30$ girls is

• A. $50$
• B. $10$
• C. $600$
• D. $1300$

Answer 1

Answer: (C)

Number of ways of selecting a boy in a class consisting of 20 boys and 30 girls
${=}^{20}{C}_1$
Number of ways of selecting a girl in a class consisting of 20 boys and 30 girls
${=}^{30}{C}_1$
Then, the total number of ways of selecting a boy and a girl from a class consisting of 20 boys and 30 girls
${=}^{20}{C}_1{\times }^{30}{C}_1$
$=20\times 30=600$