problem
Pairs of numbers
Age
5 to 7
Challenge level
If you have ten counters numbered 1 to 10, how many can you put into pairs that add to 10? Which ones do you have to leave out? Why?
problem
Eggs in baskets
Age
5 to 7
Challenge level
There are three baskets, a brown one, a red one and a pink one, holding a total of 10 eggs. How many eggs are in each basket?
problem
Sealed solution
Age
7 to 14
Challenge level
Ten cards are put into five envelopes so that there are two cards in each envelope. The sum of the numbers inside it is written on each envelope. What numbers could be inside the envelopes?
problem
Finding fifteen
Age
7 to 11
Challenge level
Tim had nine cards each with a different number from 1 to 9 on it. How could he have put them into three piles so that the total in each pile was 15?