## Resource of the Week: probability as a fraction

Probability does cause some confusion with children, partly because it can be expressed in several ways and because it is very hard to find events which are absolutely certain to happen, or not happen.

One way of displaying the probability of an event is as a percentage: for example, there is a 50% chance of landing on a head when tossing a coin.

Another way is as a fraction: there is 1/2 chance, or one in two chance of landing on heads.

A third way is as a decimal fraction, where zero means no chance and 1 is certain: there is 0.5 chance of landing on heads. Probability can be displayed along a number line marked from zero to one.

A the end of the page there is a tricky probability line where the events have to be placed in order of likelihood.

This year 6 maths worksheet is the second published which looks at probability as a fraction and then as a decimal fraction. A calculator would be useful to do the conversion and it is suggested that the answer should be displayed to 2 decimal places. A useful homework sheet.

Giving the probability as a fraction_(pg 2)

## Year 5 probability

Probability, or chance,  is one of the more misunderstood areas of maths and one which has only crept into the Primary curriculum in the last 20 years or so. It brings with it a whole new set of vocabulary and concepts which are very precise in their meaning.

By the end of year 5 children should have come across the following terms:
perhaps, might, fair, unfair, likely, unlikely, equally likely, chance, certain, uncertain, probable, possible, impossible, good chance, poor chance, no chance, equal chance, even chance, evens, fifty-fifty chance, likelihood, probability, possibility.
The first two worksheets I have published look at events which are impossible (such as my talking to Henry V111 this evening), unlikely (such as throwing a die and getting a 1), likely (such as waking up tomorrow) or certain (such as throwing a normal die and getting a number from 1 to 6). Finding events which are either certain or impossible are often much harder than you might think.

The second pair of worksheets look at events that have an even chance of happening (such as tossing a coin and getting a head). However, care has to be taken to understand that, if there are two possibilities, they are not necessarily equally likely. For example, there are two possibilities – I might buy a new Rolls Royce today or I might not. Unfortunately, these two events are not equally likely. Another example of this is I choose a number between 1 and 5. Is the number I choose a prime number? As there are three prime numbers between 1 and 5 (2, 3 and 5) and two numbers that are not, there is not an even chance that I will choose a prime number.
Sometimes further investigations have to be carried out before a probability question can be answered. Take the possibility of a factor of 16 being even. Probably the best way of doing this is to first find all the factors of 16, group them into even or odd and then work out the probability.

Go to Year 5 probability worksheets

## Year 6 maths worksheet: Probability as a fraction

Probability does cause some confusion with children, partly because it can be expressed in several ways.

One way of displaying the probability of an event is as a percentage: there is a 50% chance of landing on a head when tossing a coin.

Another way is as a fraction: there is 1/2 chance, or one in two chance of landing on heads.

A third way is as a decimal fraction, where zero means no chance and 1 is certain: there is 0.5 chance of landing on heads. Probability can be displayed along a number line marked from zero to one.

This year 6 maths worksheet is the second published which looks at probability as a fraction and then as a decimal fraction. A calculator would be useful to do the conversion and it is suggested that the answer should be displayed to 2 decimal places. A useful homework sheet.

Giving_the_probability as a fraction_(pg 2)

## Year 6 probability worksheet

This page looks at writing the probability of events happening as a fraction or a decimal fraction.

For example, the probability of getting a head when tossing a coin is 1/2, but this can also be written as 0.5

There are several things to look for on this page:

1. being able to find the probability as a fraction and then simplifying the fraction. Rolling an even number on a 1-6 die is 3/6 or 1/2.

2. being able to convert the decimal into a decimal fraction. Some of these are very easy but others, such as converting 1/52 are difficult. You may like your students to use a calculator to do this.

3. If a calculator is used, round answers to two decimal places.

Again, it is not easy to place events on the number line at the bottom of the page. The main thing to look for is that the events are in the right order and approximately in the right place.

Giving the probability as a fraction or decimal (pg1)