(Q). In the annual function of a school 10 boys & 20 girls danced such that in a particular dance only 1 boy & 1 girl participated. Total how many dance was performed?
Solution:-
In a dance we have to select one boy out of 10 boys in ¹⁰C₁ = 10 ways, and one girl oout of 20 girls in ²⁰C₁ = 20 ways,
Hence total number of dance performed = 10×20
= 200 Answer