Angela has the following coins in her pocket:

10p 1p 50p 2p 20p

She pulls out two coins at random.

a) How many different combinations of pairs of coins are the

b)

List all of the combinations,

write your answers like this: (10p, 1p)

You must write all of your answers on one line.

There are 10 different combinations

The list of different combinations is:

(10p, 1p), (10p, 50p), (10p, 2p), (10p, 20p), (1p, 50p), (1p, 2p),

(1p, 20p), (50p, 2p), (50p, 20p), (2p, 20p)

Explanation:

The possible combinations are:

1. Assuming the first coin is 10p:

(10p, 1p) (10p, 50p) (10p, 2p) (10p, 20p)

2. Asuming the first coin is 1p

Do not count (1p, 10p) as it is the same combination as (10p, 1p)

(1p, 50p) (1p, 2p) (1p, 20p)

3. Assuming the first coin is 50p:

Do not count (50p, 10p) nor (50p, 1p) as they are the same combinations (10p, 50p) and (1p, 50p) counted earlier:

(50p, 2p) (50p, 20p)

4. Assuming the first coin is 2p:

The only new combination is:

(2p, 20p)

5. All the combinations with 20p have already been listed.

Therefore:

There are 4 + 3 + 2 + 1 = 10 different combinations

The list of different combinations is:

(10p, 1p), (10p, 50p), (10p, 2p), (10p, 20p), (1p, 50p), (1p, 2p),

(1p, 20p), (50p, 2p), (50p, 20p), (2p, 20p)