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Lesson17 |
Addition & Subtraction of Fractions
Use VERTICALLY AND CROSSWISE to write the answer straight
down!
2 + 8 =
3 4
2x4 +8x3 = 8+24
=32 =16
12
12 12
6
Multiply crosswise and add to get the top of the answer:
2 x 4 = 8 and 8 x 3 = 24. Then 8+ 24= 32.
The bottom of the fraction is just 3 x 4 = 12
You multiply the bottom number together
2 + 7 =
18 +49 = 67
7
9
9 x7 63
Subtracting is just as easy: multiply crosswise as before, but subtrac
3/ 5 -2/ 6
18-10 =
8 = 4
30
30 15
Now see the addition of these compound fractions
11
+21 =
2 3
Here 1 and 2 are whole numbers and 1/2
and
1/3 are fractions .Addition of these compound fractions are quite
easy .Add whole numbers and fractions separately then
write both together
1+2 = 3 . 1 + 1 =
3+2 =5
2 3
6 6
=35
6
It is our required answer
In subtraction do as before but subtract instead of addition
5 2 - 22
=
3 4
5- 2 =3 2
- 2 = 8
- 6 = 2 =
1
3 4
12 12
6
=3 1
6
It is our required answer
Square of Fraction
To square any compound fraction containing 1/2, like 41/2
for instance
Multiply the whole number by the next higher whole
and append 1/4 to the product.
Thus, 4 1/2 x 4 1/2 = 20 1/4. (4 x (4+1) = 20; tag on 1/4 to get 20 1/4.)
Multiplication of fraction
To multiply
any two like numbers with fractions that sum to 1
6 3/4 x 6 1/4), multiply the whole number by the next highest number (6 x 7)
and append the product of the fractions (3/4 x 1/4).
In the case of 6 3/4 x 6 1/4, 6 x 7 = 42
Then append the product of 3/4 x 1/4, 3/16. Thus, 42 3/16.