Question

Fair Spinner A has four equal sections labelled 1,2,3,4.

Fair Spinner B has four equal sections labelled 2,3,4,5.

Each Spinner is spun once and the numbers added.
Work out the probability that the total is 5 or less.
Give your answer as a Fraction.

Answer 1

3/8

Explanation:

The spinner A has 4 possible values:

1, 2, 3, 4

The spinner B has 4 possible values:

2, 3, 4, 5

The possible pairs we can have are:

(1,2), (1,3), (1,4), (1,5),

(2,2), (2,3), (2,4), (2,5),

(3,2), (3,3), (3,4), (3,5),

(4,2), (4,3), (4,4), (4,5).

The sum of these pair of values are:

3, 4, 5, 6,

4, 5, 6, 7,

5, 6, 7, 8,

6, 7, 8, 9.

So we have 6 values that are 5 or less, in a total of 16 values, so the probability of the sum being 5 or less is P = 6/16 = 3/8