Page 182 - New Medley 5 Semester 1

3 7 8
(b) + +
8 12 15

Here, the LCM of 8, 12 and 15 is 120.

3 3 × 15 45
,
,
So, = = 28 12 15
8 8 × 15 120
,
24, 615
×
7 710 70 32 315
,
,
= =
×
12 12 10 120 21, 5
,
8 8 × 8 64
and = =
15 15 × 8 120
 LCM = 2 × 2 × 3 × 2 × 5 = 120

3 7 8 45 70 64
Thus, + + = + +
8 12 15 120 120 120

45 + 70 + 64 179 59
= = = 1
120 120 120
Example 7: Subtract.
8 8 3 1
(a) from (b) 2 from 4
25 15 4 2

8 8
Solution: (a) −
15 25

Here, the LCM of 15 and 25 is 75. Here, 15 = 3 × 5 and

8 8 8 × 5 8 × 3 25 = 5 × 5
∴ − = − ∴ LCM of 15 and 25
15 25 15 × 5 25 × 3 = 3 × 5 × 5 = 75

40 24 40 − 24 16
= − = =
75 75 75 75

1 3 9 11
(b) 4 − 2 = − (Change into improper fractions)
2 4 2 4
9 × 2 11
= − ( LCM of 2 and 4 is 4.)
2 × 2 4

18 11 18 − 11 7 3
= − = = = 1
4 4 4 4 4
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