SumNinja

Make subtraction easier by counting up

Instead of counting backwards, start at the smaller number and move forward to the larger one. The jumps between them give you the answer.

For 73 − 58, start at 58 and move to 60, then 70, then 73. Those jumps are 2, 10, and 3. Together they make 15, so 73 − 58 = 15. This strategy turns subtraction into small additions that are easier to do in your head.

Find the gap from 58 to 73

Start at the smaller number. Move forward in useful jumps until you reach the larger number, then add the jumps.

73 − 58 = ?
Start 58
+2 Reach the next ten
Stop 60
+10 Jump ten
Stop 70
+3 Reach the larger number
Finish 73
Add the jumps 2 + 10 + 3 = 15

73 − 58 = 15

How to calculate 83 − 67 in your head

Ask how far it is from 67 to 83. Move through round numbers so each jump is easy to remember.

  1. Reach the next ten

    67 + 3 = 70

    Start at 67. The first useful stop is 70, which is 3 away.

  2. Jump to 80

    70 + 10 = 80

    A jump of 10 is quick to calculate and easy to keep in your head.

  3. Finish at 83

    80 + 3 = 83

    The final jump from 80 to the larger number is 3.

  4. Add the jumps

    3 + 10 + 3 = 16

    You moved forward by 16 altogether, so 83 − 67 = 16.

Three more examples

The jumps can be different sizes. Choose round-number stops that make the calculation easy to follow.

63 − 58

58 → 60 (+2) → 63 (+3)

= 5

92 − 76

76 → 80 (+4) → 90 (+10) → 92 (+2)

= 16

100 − 87

87 → 90 (+3) → 100 (+10)

= 13

Choose jumps you can remember

You do not need to count every number. Use a few larger jumps that keep the calculation clear.

Reach the next ten

From 58, jump 2 to reach 60. Round numbers are useful places to stop.

Use tens when you can

From 60, a jump of 10 reaches 70 without changing the ones digit.

Finish with the ones

From 70, only 3 more is needed to reach 73. Add all three jumps at the end.

Now try 81 − 68

81 − 68 = ?

Start at 68. Which round numbers could you use on the way to 81?

Show the answer Hide the answer
13

Move 68 → 70 (+2), 70 → 80 (+10), and 80 → 81 (+1). The jumps add up to 13.

When counting up is useful

Use this strategy when you want to find the difference between two amounts, especially when the smaller number is close to a round number.

Compare scores

One score is 58 and another is 73. Count up from 58 to see that the difference is 15.

See what remains

You have completed 67 of 83 questions. The jumps from 67 to 83 show that 16 remain.

Check change

An item costs $67 and you pay with $80. Count up from 67 to 80 to see that the change is $13.

Try counting up while you play

For each subtraction, start at the smaller number and move forward in useful jumps. Add the jumps when you reach the larger number.

Practise subtraction

Questions about counting up for subtraction

Why does counting up work for subtraction?

Subtraction finds the difference between two numbers. Counting forward from the smaller number measures that same difference.

When should I use this strategy?

It is especially useful when the numbers are fairly close or the smaller number is near a round ten. If another method feels clearer for a calculation, use that instead.

Is this really subtraction if I am adding?

Yes. You are using addition to find a missing amount. For example, 67 + 16 = 83, so 83 − 67 = 16.

Do I need to count every number?

No. Jump to useful round numbers such as 60, 70, or 100. A few larger jumps are faster and easier to remember than counting by ones.