How many to be sure? (logic)
Things of 2 to 4 colours are mixed up in a drawer, bag or jar, and someone takes them out without looking. The student works out the smallest number they must take to be sure of two, or three, of the same colour, or how many more they need when a few are already out.
The trick is to plan for the unluckiest grabs: one of every colour can come out before anything matches, so the answer is one more than that. How many there are of each colour makes no difference, which is the trap. The working shows the unlucky grabs one at a time.
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What changes each time
- Two the same, three the same, or how many more
- 2 to 4 colours, with 3 to 10 of each
- Socks, marbles, beads, crayons, pencils and more
More patterns, sequences and logic practice
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- Repeating patterns (Grade 1)
- Hundred chart: 10 more and 10 less (Grade 1)
- Number sequences (Grade 2)
- Number machines (Grade 2)
- Multiples on a hundred chart (Grade 3)
- Ordering from clues (logic) (Grade 3)
- Truth-tellers and fibbers (logic) (Grade 3)
- Logic grid puzzles (Grade 3)
- Take-away game (logic) (Grade 4)
- Cook it faster (Grade 5)
- Growing patterns (Grade 4)
- Doubling every day (Grade 4)
- Bigger start or bigger raise? (Grade 4)