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Just a few slides on a quick short cut to adding fractions. Used with science students who needed a revision session.
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You can add two fractions by doing three multiplications and an addition!
€
3
5+2
3
€
3
5+2
3
€
3
5+2
3
€
3
5+2
3
€
3
5+2
3
€
3
5+2
3
3 3
€
3
5+2
3
9
€
3
5+2
3
9
€
3
5+2
3
9 5 2
€
3
5+2
3
9 10
€
3
5+2
3
9 10
€
3
5+2
3
9 10
5 3
€
3
5+2
3
9 10
15
€
3
5+2
3
9 10
15
+
€
3
5+2
3=19
15
9 10
15
+
€
3
5+2
3=14
15
An example that has denominators with a common factor…
€
5
6+4
9
€
5
6+4
9
€
5
6+4
9
5 9
€
5
6+4
9
45
€
5
6+4
9
45
€
5
6+4
9
45 24
€
5
6+4
9
45 24
€
5
6+4
9
45 24
54
€
5
6+4
9
45 24
54
+
€
5
6+4
9=69
54
45 24
54
+
€
5
6+4
9=69
54
€
5
6+4
9=115
54
€
5
6+4
9=115
54
5
€
5
6+4
9=115
54
5
18
€
5
6+4
9=15
18
You had to cancel down at the end because of the common factor…
Mixed numbers?
Mixed numbers?Just convert to improper fractions and carry on…
Subtraction?
Subtraction?Just subtract the top totals instead of adding…
Your turn…
€
4
5+7
2Answer on next slide…
€
4
5+7
2= 4
3
10
Make up some more questions and check them with your calculator
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