Probability
PROBABILITY
PROBABILITY is usually written as a FRACTION
(Sometimes decimals or % may be used)
NEVER USE RATIO for probability
e.g. 2 : 5 x This will ALWAYS be WRONG
Two boxes contain coloured blocks as shown below:
Try to
simplify
fractions
1.
2.
𝟏
𝟐
𝟏
Box A: p(Pink) =
Box B: p(Pink) = =
𝟓
𝟖 𝟒
Paul has to choose one block at random.
He wants it to be yellow.
Which box should he pick from? Explain your choice.
Method 1: Make the denominators the same
Box A: p(Yellow) =
Box B: p(Yellow) =
𝟐
𝟓
𝟑
𝟖
=
=
𝟏𝟔
He should
use Box A
𝟒𝟎
𝟏𝟔
𝟏𝟓
𝟒𝟎
𝟒𝟎
>
𝟏𝟓
You must
show your
method
𝟒𝟎
Method 2: Change each fraction to decimal
Numerator
divided by
denominator
© www.teachitmaths.co.uk 2017
Box A: p(Yellow) =
𝟐
Box B: p(Yellow) =
𝟑
26848
𝟓
𝟖
= 0.400
= 0.375
He should
use Box A
0.4 > 0.375
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