# Probability

### 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

1. a prime number
2. a composite number
3. 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

1. a square number
2. 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

2. of black king
3. of club
4. of jacks

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

Two different dice are tossed together. Find the probability:

1. of getting a doublet
2. 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:

1. divisible by 8
2. 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

1. even sum
2. even product