Mental Math - Subtraction

This video tutorial teaches a strategy for simplifying mental subtraction by using expanded form. It demonstrates how to break down numbers into parts, subtracting each part separately. The method is effective when the minuend is a multiple of 10. For non-multiples, the video explains how to adjust both numbers to make the minuend a multiple of 10, then apply the same strategy. The tutorial concludes with a summary of the mental subtraction techniques covered.

What is the first step in simplifying the subtraction of 140 - 68 using expanded form?

• Add 60 to 140

• Add 8 to 140

• Subtract 60 from 140

• Subtract 8 from 140

When using the strategy on 124 - 67, what adjustment is made to the minuend to make it a multiple of 10?

• Add 6 to 124

• Subtract 6 from 124

• Subtract 7 from 124

• Add 7 to 124

After adjusting 124 and 67 to 130 and 73 respectively, what is the next step in the subtraction process?

• Subtract 3 from 60

• Add 70 to 130

• Subtract 70 from 130

• Add 3 to 60

What is the result of subtracting 60 from 130 in the adjusted subtraction problem?

• 73

• 57

• 60

• 70

What is the main strategy discussed in the lesson for calculating differences mentally?

• Using a calculator

• Rounding numbers to the nearest hundred

• Using expanded notation and adjusting numbers

• Adding numbers instead of subtracting