Measurement
Money problems
Add, subtract and multiply amounts of money, and work out the change from a payment.
Money problems are ordinary arithmetic with a price attached, and the hard part is almost never the sum — it is deciding which sum to do. Things bought together are added. Several of the same thing are multiplied. A comparison between two prices is a subtraction. And change is a subtraction too, but only after the total cost is known.
Change is the last step, never the first
When several things are bought and one payment is made, there are always two steps. Work out what everything costs altogether, and only then take that away from what was handed over. Taking the payment away from one item's price is the commonest wrong turn in this whole topic.
Worked example
A book costs $135 and you pay with $200. How much change do you get?
Count on from 135 to 140.
Getting to a tidy number first makes the rest easy — that is 5 so far.
Try it together
Now let us buy three tickets together.
Each ticket costs $75, and you hand over $250.
1.First the total. What is 3 × 75?
Have a go
Have a go on your own: a cap costs $140 and you pay with $500. How much change do you get? Give just the number.
Hint: Count on from the price up to the amount you handed over.
Ready to practise?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.