Lesson 25 Section 2 SUBTRACTING MIXED NUMBERS
Solution. In this example, we may simply subtract the whole numbers and subtract the fractions -- similarly to adding mixed numbers.
But consider the following, in which the fractions are reversed:
To see how to deal with it, consider the following: ![]() We cannot take 40 minutes from 10 minutes -- we need more minutes. To get them, we will break off 1 of the 7 hours, and decompose it into 60 minutes. We then regroup them with 10 minutes. 60 minutes + 10 minutes = 70 minutes: ![]() 2 hours from 6 hours is 4 hours. 40 minutes from 70 minutes is 30 minutes. ![]() Solution. We cannot take 11 inches from no inches. To make inches, then, from 8 feet we will take 1 foot -- which is 12 inches: ![]() 5 feet from 7 feet is 2 feet. 11 inches from 12 inches is 1 inch. We can now return to our problem:
We need more fifths. Where will we get them? From 8. We will break off 1 from 8, and decompose it into
We will then add those Then:
* Actually, the simplest way to do this problem is mentally, by rounding off
1 8 ![]()
Now the mystery, if any, is: How does that numerator get to be 9? 9 is the sum of the original numerator 1 and denominator 8: ![]()
7 is the sum of denominator plus numerator: 5 + 2.
![]()
Again, the simplest way to do this is mentally by rounding off 1 The problem then becomes 6 − 1
Solution. According to the meaning of subtraction,
Compare Lesson 7, Example 2.
Solution. First, we must make the denominators the same:
We cannot take
Mentally:
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