Coin Multiplication

Children recognise the coins that we use every day. Coin Multiplication teaches them to take a number (usually a 2d number) and then find the 1st, 2nd, 5th, 10th, 20th, 50th and 100th multiples of that number. If we include the £2 coin on our coin card, that means they find the 200th multiple as well. Our job is to show children how all of these multiples can be found simply by:

• multiplying by 10,
• halving and
• doubling.

Step 1

The first of the 5 steps for Coin Multiplication introduces us to a ‘1, 10 Card’ and shows us how to set it out. The 1^st multiple is the number itself and the 10^th multiple is the number itself, but this time made 10 times bigger.

Step 2

The second step extends the ‘1, 10 card’ idea to produce a ‘1, 2, 5, 10 card’. Start with ‘easy’ numbers that lend themselves to getting the correct answers.

• Start as before by using the 1^st multiple to find the 10^th multiple
• Find the 2^nd multiple by doubling the 1^st multiple
• Find the 5^th multiple by halving the 10^th multiple

Well done! This is a completed ‘1, 2, 5, 10’ Coin card. Keep practicing with a 1, 2, 5, 10 (spaces added) card until you can complete quickly (without having to use their fingers) delete before attempting the next step.

Step 3

Now we extend the same ideas to write out a ‘Full Coin Card’. This includes using the 2^nd multiple to find the 20^th, using the 5^th multiple to find the 50^th. Then using the 1^st multiple to find the 100^th, and the 2^nd to find the 200^th. Once we have written out all these multiples (1^st, 2^nd, 5^th, 10^th, 20^th, 50^th, 100^th and 200^th) then we have a ‘Full Coin Card’! Congratulations! Now, practise with lots of different starting numbers (mainly using 2 digit whole numbers). The challenge is to be able to write a Full Coin Card like this for any 2 digit number in less than 60 seconds! Remember to always fill in the multiples in this order: 1^st, 10^th, 2^nd, 5^th, 20^th, 50^th, 100^th.

Step 4

Once you can write out a ‘Full Coin Card’ fluently, try adding 2 of the coin multiples together. For example, you can find the 21^st multiple by adding the 20^th and 1^st multiples together, or find the 52^nd multiple by adding the 50^th and 2^nd multiples together. Try finding different variations of which multiples you can find, and combing this with different starting numbers.

Step 5

At Step 5 we add 3 different coin multiples together. For example, you can find the 121^st  multiple by adding the 100^th, 20^th and 1^st multiples together, or find the 252^nd multiple by adding the 200^th, 50^th and 2^nd multiples together.