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To add a one-digit number to a two-digit number, start with the bigger number and count forwards with the smaller number.

43 (larger number) + 8 (smaller number) = 51

You could find the number on a number square and count forwards. Find number 43, then count forwards 8 ones to get 51.

Subtracting a one-digit number from a two-digit number

To subtract a one-digit number from a two-digit number, you also start with the bigger number, but you count backwards.

Try it on the 100 square above.

43 - 8 = 35

When a number problem uses two two-digit numbers, we break down the numbers into tens and ones.

55 + 34 = ?

Start with the tens and add them together.

5 tens + 3 tens = 8 tens

or

50+ 30 = 80

Then add the ones.

5 ones + 4 ones = 9 ones

or

5 + 4 = 9

Finally add both answers together.

80 + 9 = 89

To subtract a two-digit number from a two-digit number we count back the tens of the smaller number and then count back the ones.

What is 58 – 44 = ?

44 has 4 tens so we count back 4 tens from the bigger number 58.

58 count back 4 tens:

58, 48, 38, 28, 18

Finally use this answer and then count back the ones:

18 – 4 = 14

Therefore:

58 – 44 = 14

Top tip!

You can use a one hundred square to help you count backwards and forwards.

Get a piece of paper and a pencil, then listen to this quiz. You only have 10 seconds to answer each question so write the answers down quickly!

Finished? Check your answers . The questions are also written out, if you can't listen to the quiz out loud.