## Supermarket sweep

By David, 24 February 2015 Activity

Bored at the supermarket? This game will have your brain churning!

### You will need

Look down the aisle and choose a price tag.

- Pen and notepad
- Supermarket
- Someone to play with (optional)

### What to do

The aim of this activity is to write down prices of items, so the total is close to $10.

- Choose an aisle in the supermarket.
- Start at one end of the aisle and walk slowly down it.
- Look at the prices of the items and choose some prices to write down.
Write down the prices you choose.

- You can only write each price once – no repeats.
- You can only go one way down the aisle. Don’t go back and write a price from earlier in the aisle.
- You can’t cross out prices you’ve chosen.
- At the end of the aisle, add up your list. Closest to $10 wins!

### Additional rules

To make the game harder, try these extra rules:

- All prices you write down have to have dollars and cents. No whole numbers of dollars allowed!
- No item can be worth more than $3.50.
- Try to get as close to $10 as possible, but if you go over, you lose!
Look for shelves with lots of prices.

### What’s happening?

There are plenty of mental tricks you can use to get better at this game. One good starting strategy is to only pick prices that end in 95 cents. You can round the prices off and keep a tally in your head, aiming for a $10 total. When you add the actual prices, the total will be just a little bit less than $10.

As you practice, you’ll get better at holding the numbers in your head. Eventually, you’ll be able to keep the exact total in your head without calculating it with a pencil or calculator. The game can still be challenging though – it takes good planning, and often a bit of luck, to get exactly $10.

At the end of the aisle, add up your prices and see how close to $10 you got!

Being able to add and subtract money in your head is a very useful skill. Many people will have a job at a cash register at some point in their lives. Being able to add and subtract in your head helps when you need to give change, and when you make a mistake with your register.

You can also use mental arithmetic when you’re buying things – making sure you have enough money when you get to the counter, and checking you get the right change.

*If you’re after more maths activities for kids, subscribe to Double Helix magazine!*

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