Question

There are $60$ boys and $40$ girls in a class. A student is selected at random. Find the probability that sudent is a girl.

Answer 1

Given in a class they are $60$ boys and $40$ girls

no of ways a student is selected ${=}^{100}{C}_1$

no of ways a girl is selected ${=}^{40}{C}_1$

Probability that selected student is a girl $=\frac{{}^{40}{C}_1}{{}^{100}{C}_1}=\frac{40}{100}=\frac{2}{5}$