Page 80 - classs 6 a_Neat

3 1 1 Short Method
EXAMPLE 8. Three boxes weigh 18 kg. 7 kg and 10 kg respectively.
A porter carries all the 4 2 5 LCM of 8 and 12 = (4 × 2 × 3) = 24. {[24 ÷ 8 = 3, 3 × 7 = 21] and [24 ÷ 12 = 2, 2 × 5 = 10]}

three boxes. What is the total weight carried by the porter?
SOLUTION: Total weight carried by the porter EXAMPLE 3. Subtract .
( 18 3 kg + 7 1 kg + 10 1 kg ) 1 5 31 32 LCM of 6, 9 = (3 × 2 × 3) = 18.
{[18 ÷ 6 = 3, 3 × 31 = 93] and
4
5
2
( 75 15 51 ) ( 375 + 150 204 ) 5 6 - 3 6 = 6 - 9 [18 ÷ 9 = 2, 2 × 32 = 64]}
= 4 + 2 + 5 kg = 20 kg 93 - 64
729 9 = 18
= 20 kg = 36 20 kg 29 11

Hence, the total weight carried by the porter is. 36 9 kg. = = 1
20 18 18
7 1 LCM of 5, 10 = (5 × 2) =1 0.
EXAMPLE 4. Subtract from 4
SUBTRACTION OF FRACTIONS 10 5
1 7 21 7
SUBTRACTION OF LIKE FRACTIONS 4 5 - 10 = 5 - 10
42 - 7
(Difference of their numerators) =
RULE Difference of like fractions = 10
(Common denominator) 35 7 7 1
= = = 3
EXAMPLE 1. Find the difference: 10 2 2
2
5 2 11 7
(i) - (ii) - 5
9 9 12 12 EXAMPLE 5. Subtract 1 from 8.
SOLUTION: we have 6

5 2 5 - 2 3 1 1 SOLUTION: We have: {[10 ÷ 5 = 2, 2 × 21 = 42) and [1 0 ÷ 10 = 1. 1 × 7 =71}
(i) - = = = 5 11
9 9 9 9 3 3 8 - 1 6 = 8 - 6

11 7 11 - 2 4 1 1 8 11 [LCM of 1, 6 = 6]
(ii) - = = = = -
12 12 12 12 3 1 6 {[6 ÷1 = 6, 6 × 8 = 48) and
3
48 - 11 [6 ÷ 6 = 1, 1 × 11 = 111}
=
SUBTRACTION OF UNLIKE FRACTIONS 6
37 1
= = 6
RULE Change the givenfractions into equivalent like fractions and then subtract. 6 6

7 5
EXAMPLE 9: Find the dlfference: -
18 12
SOLUTION: LCM of 8 and 12 = ( 4 × 2 × 3) = 24.

7 = 7 × 3 = 21 and 5 = 5 × 2 = 10 .
8 8 × 3 24 12 12 × 2 24

7 - 5 = 21 - 10 = 21 .
8 12 24 24