Question

A box contains 90 discs which are numbered from 1 to 90. If one disc is drawn at random from the box, find the probability that it bears a perfect square number.

Answer 1

Total number of discs = 90

Let E₂ be the event of getting a perfect square number.

Discs bearing perfect square numbers are 1, 4, 9, 16, 25, 36, 49, 64 and 81.

Number of discs bearing a perfect square number = 9

∴ P(getting a perfect square number) =

P(E₂) = `("Number of outcomes favourable to E"_2)/"Number of all possible outcomes"`

P(E₂) = `9/90`

∴ P(E₂) = `1/10`

Thus, the probability that the disc bears a perfect square number is `1/10`