Probability (C10)

Classical definition of probability. Simple problems on finding the probability of an event.

The probability of selecting a blue marble at random from a jar

The probability of selecting a blue marble at random from a jar that contains only blue, black and green marbles is 1/5. The probability of selecting a black marble at random from the same jar is 1/4 . If the jar contains 11 green marbles, find the total number of marbles in the jar.

A box contains cards numbered from 1 to 20. A card is drawn at random

A box contains cards numbered from 1 to 20. A card is drawn at random from the box. Find the probability that number on the drawn card is

a prime number
a composite number
a number divisible by 3

A box contains cards numbered 11 to 123. A card is drawn at random from the box

A box contains cards numbered 11 to 123. A card is drawn at random from the box. Find the probability that the number on the drawn card is

a square number
a multiple of 7

A box contains 12 balls of which some are red in colour

A box contains 12 balls of which some are red in colour. If 6 more red balls are put in the box and a ball is drawn at random, the probability of drawing a red ball doubles than what it was before. Find the number of red balls in the bag.

The King, Queen and Jack of clubs are removed from a pack of 52 cards

The King, Queen and Jack of clubs are removed from a pack of 52 cards and then the remaining cards are well shuffled. A card is selected from the remaining cards. Find the probability of getting a card

of spade
of black king
of club
of jacks

Two different dice are tossed together. Find the probability of getting a doublet

Two different dice are tossed together. Find the probability:

of getting a doublet
of getting a sum 10, of the numbers on the two dice

An integer is chosen at random between 1 and 100

An integer is chosen at random between 1 and 100. Find the probability that it is:

divisible by 8
not divisible by 8

A bag contains 15 white and some black balls

A bag contains 15 white and some black balls. If the probability of drawing a black ball from the bag is thrice that of drawing a white ball, find the number of black balls in the bag.

Two different dice are thrown together

Two different dice are thrown together. Find the probability that the numbers obtained have

even sum
even product