Addition and subtraction within 20

First add the two numbers in the question. Then look at the equations in the answers.

In the correct equation, the number after = is the sum you found. Both sides of an equation must show the same amount.

The passengers who got off are no longer on the bus. Subtract the number who got off from the starting number of passengers.

Check: the passengers left and the passengers who got off must add up to the starting number.

Add the second number to the first. You can count forwards one at a time.

If you cross 10, it can help to reach 10 first, then add the rest. For example, 8 + 5 = 8 + 2 + 3 = 13.

Find how much more to add to reach the number after the equals sign.

1. Start with the number you know.
2. Count forwards to the total and count your steps.
3. The number of steps belongs in the blank.

You can also subtract the known number from the total. Check by adding.

Subtract the second number from the first. You can count backwards one at a time.

If you cross 10, it can help to reach 10 first, then subtract the rest. For example, 13 − 5 = 13 − 3 − 2 = 8.

The blank shows how much was taken away, and the number after = shows how much remains.

1. Subtract the amount remaining from the starting number.
2. Put the result in the blank.
3. Check: subtracting your answer from the starting number must give the remainder shown.