Question

A natural number is chosen at random for amongst first 300.What is probability that the number is chosen divisible by 3 or 5?

Answer 1

Dear student
$$\begin{gathered} \mathrm{From}1\mathrm{to}300,\mathrm{number}\mathrm{multiple}\mathrm{of}3=3,6,9,12,....,300=100\mathrm{numbers} \\ \mathrm{From}1\mathrm{to}300,\mathrm{number}\mathrm{multiples}\mathrm{of}5=5,10,15,...,300=60\mathrm{numbers} \\ \mathrm{So},\mathrm{total}\mathrm{numbers}\mathrm{which}\mathrm{are}\mathrm{multiples}3\mathrm{or}5=100+60 \\ \mathrm{Hence}\mathrm{probability}=\frac{\mathrm{Number}\mathrm{of}\mathrm{favourable}\mathrm{events}}{\mathrm{Number}\mathrm{of}\mathrm{sample}}=\frac{160}{300}=\frac{8}{15} \end{gathered}$$
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