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May 2013

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The ideas in this fraction lesson are taken from Math Mammoth Fractions 1 book. Only a few examples of each problem type are shown; you should make more problems of each kind for the student.

Subtracting mixed numbers
Free lesson plan from HomeschoolMath.net

1. Warm-up: see if you can subtract mixed numbers!

Shade 2 3 4 .  Cross out 1 1 4 a.   2 3 4 − 1 1 4 =		Shade 2 1 8 .  Cross out 5 8 b.   2 1 8 − 5 8 =
Shade 2 3 7 .  Cross out 1 6 7 c.   2 3 7 − 1 6 7 =		Shade 2 1 2 .  Cross out 1 2 3 . (Hint: change these into sixth parts.) d. Challenge.  2 1 2 − 1 2 3 =

 

Strategy 1: Subtract whole-number parts and the fractional parts separately. This is natural to do, and works well when the subtrahend (number you subtract) has a smaller fractional part than the minuend.       6  7 8 −   3  2 8 3   5 8

2. Subtract.

1  3 4 −   1  1 4     a.  Cross out 1 1/4.		c.   11  7 9 −   4  3 9
e.   5 6 11   −   3 2 11   =	f.  6 2 7   −  1 2 7   =

Strategy 2: Subtract in Parts First subtract what you can from the fractional part of the minuend. Then subtract the rest from one of the whole pies. The examples will help you understand this.
2 1 8  −  5 8 = ?    We can't subtract 5/8 from 1/8. So, first subtract only 1/8, which leaves 2 whole pies. The rest (4/8) is subtracted from one of the whole pies.    2 1 8  −   5 8  =   2 1 8  −   1 8  −   4 8  =            =     2    − 4 8  =  1 4 8	3 2 9  − 2 7 9 = ?   We can't subtract 7/9 from 2/9. So, first subtract 2 2/9, which leaves 1 whole pie, and the rest (5/9) is subtracted from the last whole pie.    3 2 9  −  2 7 9  =   3 2 9  −  2 2 9  −   5 9  =            =     1    − 5 9  =  4 9

3. Subtract in parts. Remember: you can add to check a subtraction problem.

4. Subtract in two parts. Write a subtraction sentence.

a.      Cross out 1 2 3 .
	d.     Cross out 1 5 7
e.     Cross out 1 7 8 .
k.     Cross out 3 4 5 .

Next lesson: part 2

The ideas in this fraction lesson are taken from Math Mammoth Fractions 1 book. Only a few examples of each problem type are shown; you should make more problems of each kind for the student.