There are 11 animals in the paddock, some of them pigs and some of them ducks. They have a total of 28 legs. How many ducks are there?
Solution
There are 3 pigs and 8 ducks in the paddock.
There are many ways to do this problem. You could use a table or you could guess and improve. If your first guess was 5 pigs and 6 ducks then there would be 32 legs. So you need fewer legs. Ducks have fewer legs so you need more ducks.
You might try drawing a diagram. Draw circles to represent the 11 animals, then give each animal 2 legs because both ducks and pigs have at least 2 legs. You only have 6 legs left to put on animals so three of them get 2 more legs, making 3 pigs and 8 ducks.
Extension
Try making up your own pigs and ducks problems. Maybe you could challenge someone else in your class.