Word Problems And Stats

Question 1

“AND” probabilities…

Answer 1

…use the words AND or BOTH
…happen IN A ROW
…happen AT THE SAME TIME

Question 2

“OR” probabilities…

Answer 2

…use the word OR

…use the phrase AT LEAST

Question 3

Ask at the start of every OR question

Answer 3

Can both events occur?

Question 4

OR probabilities:

If the answer is YES - the events can happen at the same time.

Answer 4

…This means the events are INDEPENDENT.

(1) add the probabilities that either happens
(2) subtract the probability that BOTH event occur

Question 5

Complements

Answer 5

Determine the probability of the opposite of what you’re looking for, and subtract it from 1 to get what you’re looking for

Question 6

“At Least Once” shortcut

Answer 6

Odds of an Event + Odds of its Complement = 1

At least once = 1-Never

Question 7

Rate problems

Answer 7

Rate X Quantity (e.g. Time) = Work (or Distance)

Question 8

Proportion rate problem

Answer 8

LABEL each item within the proportion. Then cross-multiply to solve the equation.

But be careful of inverse relationships. In these cases, set the products of the quantities equal to each other and solve.

Question 9

1 kilometre = how many meters?

Answer 9

1,000 meters

Question 10

1 meter = how many centimetres?

Answer 10

100 cm

Question 11

1 centimetre = how many millimetres?

Answer 11

100 millimetres