Video: Subtracting Multiples of 10 along a Number Line

Subtract 30 from 78. Use the number line to help you.

01:31

Video Transcript

Subtract 30 from 78. Use the number line to help you.

We can see from the number line that subtracting 30 is the same as taking away three lots of 10. We’re starting at 78. Let’s take away one lot of 10. 78 has seven tens. If we take away one ten, then it will have six tens. 78 take away 10 is 68. Now we’re on 68. We have to take away 10 again. 68 has six tens. If we take away one ten, we’ll have five tens. 68 take away 10 is 58. We just have one more lot of 10 to take away. 58 take away 10 is 48. Five tens take away one ten leaves us with four tens. We used the number line to subtract three tens, or 30, from 78. The answer is 48. 78 subtract 30 is 48.

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