The weight of 72 books is 9 kg.
(a) Find the weight of 80 such books.
(b) How many books will weigh 6 kg?
Answers
Answer:
We can solve this problem by Proportions
Step-by-step explanation:
(a) Weight of 80 books
Weight (in kg) No. of books
9 kg 72
x kg 80
9 : x :: 72 : 80
By multiplying the first and last and the middle ones. We get,
9 × 80 = 72x
9 × 80 / 72 = x
10 = x
So, the weight of 80 books is 10 kg
(b) How much books would weigh 6 kg
Weight (in kg) No. of books
9 kg 72
6 kg x
9 : 6 :: 72 : x
By multiplying the first and last and the middle ones. We get,
9x = 72 × 6
x = 72 × 6 / 9
x = 8 × 6
x = 42
So, the weight of 42 books will be 6 kg
(a) The weight of 72 books is 9 kg
==> The weight of one book is 9 kg / 72
The weight of 80 books is 9 kg / 72 * 80
==> 9 kg / 72 * 80
==> 9 kg / 9 * 10
==> 1 kg * 10
==> 10 kg
The weight of 80 books is 10 kg
(b) The weight of one book is 9 kg / 72 [ From (1) ]
Let x books weigh 6 kg
Now x books weigh 9 kg / 72 * x
According to the problem:
9 kg / 72 * x = 6 kg
==> 9 x / 72 = 6
==> x = 6 * 72 / 9
==> x = 6 * 8
==> x = 48
The number of books are 48
( * this mark means multiplication sign )
hope this helps u