EASY
AS and A Level
IMPORTANT
Earn 100

Two ordinary fair dice are rolled. The discrete random variable X is the lowest common multiple of the two numbers rolled.

Find E(X) and PX>E(X).

Important Questions on Probability Distributions

EASY
AS and A Level
IMPORTANT

Two ordinary fair dice are rolled. The discrete random variable X is the lowest common multiple of the two numbers rolled.

Calculate Var X.

EASY
AS and A Level
IMPORTANT

In a game, a player attempts to hit a target by throwing three darts. With each throw, a player has a 30% chance of hitting the target.

Draw up the probability distribution table for H, the number of times the target is hit in a game.

EASY
AS and A Level
IMPORTANT

In a game, a player attempts to hit a target by throwing three darts. With each throw, a player has a 30% chance of hitting the target.

How many times is the target expected to be hit in 1000 games?

EASY
AS and A Level
IMPORTANT

Two students are randomly selected from a class of 12 girls and 18 boys.

Find the expected number of girls and the expected number of boys.

EASY
AS and A Level
IMPORTANT

Two students are randomly selected from a class of 12 girls and 18 boys.

Write the ratio of the expected number of girls to the expected number of boys in simplified form. What do you notice about this ratio?

EASY
AS and A Level
IMPORTANT

Two students are randomly selected from a class of 12 girls and 18 boys.

Calculate the variance of the number of girls selected.

EASY
AS and A Level
IMPORTANT

A sewing basket contains eight reels of cotton: four are green, three are red and one is yellow. Three reels of cotton are randomly selected from the basket.

Show that the expected number of yellow cotton reels is 0.375.

EASY
AS and A Level
IMPORTANT

A sewing basket contains eight reels of cotton: four are green, three are red and one is yellow. Three reels of cotton are randomly selected from the basket.
Find the expected number of red cotton reels.