Mastering Probability Concepts

What is the probability of rolling a sum of 7 with two six-sided dice?

• 1/12

• 1/4

• 1/6

• 1/8

Answer explanation

There are 6 out of 36 ways to sum to 7.

1+6, 2+5, 3+4, 4+3, 5+2 and 6+1

Calculate the probability of drawing an ace from a standard deck of 52 playing cards.

• 1/26

• 1/52

• 2/13

• 1/13

Answer explanation

4 Aces out of 52 cards

If a bag contains 3 red, 5 blue, and 2 green marbles, what is the probability of drawing a blue marble?

• 1/2

• 3/10

• 2/5

• 1/3

How many different ways can you arrange the letters in the word 'MATH'?

• 18

• 24

• 6

• 12

Answer explanation

4x3x2x1

A box contains 4 white and 6 black balls. If two balls are drawn at random, what is the probability that both are black?

• 1/3

• 3/10

• 1/2

• 2/5

Answer explanation

First marble not replaced so

6/10 X 5/9

In a survey of 100 people, 60 like tea, 40 like coffee, and 20 like both. What is the probability that a randomly selected person likes tea or coffee?

Recommendation: Draw a Venn Diagram

• 0.8

• 0.9

• 0.6

• 0.5

What is the sample space for flipping a coin twice?

• {HHH, HHT, HTH, HTT, THH, THT, TTH, TTT}

• {HH, HT, TH}

• {H, T}

• {HH, HT, TH, TT}

What is the probability of getting at least one head when flipping a coin three times?

The opposite to "at least" is often easier to find.

NB The opposite to "at least one" is none.

• 7/8

• 1/2

• 1/4

• 3/8

Answer explanation

P(at least one) = 1 - P(none)

1 - 1/8 = 7/8

If the probability of rain tomorrow is 0.3, what is the probability that it will not rain?

• 0.1

• 0.5

• 0.7

• 0.9

Answer explanation

P(not rain) = 1 - P(rain)

1 - 0.3 = 0.7

In a class of 25 students, 10 are studying Maths, 15 are studying Physics, and 5 are studying both. What is the probability that a randomly selected student is studying Maths or Physics?

• 0.6

• 0.4

• 0.9

• 0.8