Logic & puzzles • Classes 6–8
How many different lunches?
Count every choice once, without missing a combination.
Take your time. Speak, draw or write your answers.
Here is what is happening.
When each of m first choices can pair with each of n second choices, there are m × n pairs. A table or tree diagram helps avoid omissions and repeated counting. Restrictions can change the total.
Your little investigation
What you need
Paper. Imagine two breads and three fillings; no real food is required.
Label breads A and B; fillings 1, 2 and 3.
Write all pairs systematically: A1, A2…
Cross out B3 as unavailable and count again.
With every pairing allowed, how many combinations are there?
KEEP ASKING
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