Q10 of 54 Page 320

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

a number divisible by 5.

There are 90 discs in a box.

⇒ Number of outcomes in which discs is selected = 90.


⇒ Number of multiples of 5 from 1 to 90.


⇒ (5,10,15,20,25,30,35,40,45,50,55,60,65,70,75,80,85,90)


⇒ Number of favourable cases = 18


⇒ Probability that disc bears number divisible by 5 –


⇒ P(number divisible by 5) =


⇒ P(number divisible by 5) =


⇒ P(number divisible by 5) =


∴ Probability that disc bears a number divisible by 5 is .


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