2.3 Systematic listing strategies — Practise with help
Try each question first. Open a hint if needed, then check the full working.
Warm-up: remember
- List the factors of 10.
- Work out .
Answers
- .
- .
Practise with help
1. A top can be red or yellow, and a base can be square or round. List every outfit.
Hint
Keep the top fixed while listing each base, then move to the other top.
Next step
With red: red-square and red-round. Now do the same with yellow.
Full working
The outfits are red-square, red-round, yellow-square and yellow-round. There are four outcomes.
2. Make three-digit numbers using 1, 2 and 3 once each. List them in order.
Hint
Group the numbers by their hundreds digit.
Next step
Starting with 1 gives 123 and 132. Repeat with 2 and 3.
Full working
The list is . Each first digit has two possible orders for the remaining digits.
3. A lunch has a choice of soup or salad and apple, pear or banana. List the meal choices.
Hint
For each first choice, list every fruit.
Next step
Soup pairs with all three fruits; salad also pairs with all three.
Full working
Soup-apple, soup-pear, soup-banana, salad-apple, salad-pear, salad-banana. There are six choices.