Multiplication and times tables · Usually met around P2
How many combinations
Each with each: tops × skirts.
How to do it
Method
Each with each: tops × skirts
3 tops × 4 skirts = 12 outfits
Another way
List them in order
A1 A2 A3 A4 / B1 B2 B3 B4 / C1 C2 C3 C4
In full
Every top can go with every skirt. Fix one top and count the skirts it can go with; every top has the same number, so 3 tops and 4 skirts give 3 lots of 4: 3 × 4 = 12 outfits. Or list them in order: top A with skirts 1, 2, 3, 4, then top B with 1, 2, 3, 4… nothing missed, nothing twice. Or draw a table with the tops as rows and the skirts as columns: each square is one outfit.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
There are 5 tops and 5 skirts. One top goes with one skirt. How many outfits are there?
Show the answer and working
Answer: 25
Each top goes with 5 skirts, so 5 tops give 5 lots of 5: 5 × 5 = 25.
Example 2
There are 18 outfits from 6 tops, each top with one skirt. How many skirts are there?
Show the answer and working
Answer: 3
6 tops, each with the same skirts: 6 × □ = 18, so there are 3 skirts.
Example 3
6 tops and 2 pairs of trousers, one top with one pair: that makes 14 outfits.
True or false?
Show the answer and working
Answer: False
Each top goes with 2 pairs, so 6 tops make 6 × 2 = 12.
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