Question

Some chairs are arranged in 3 rows in a class.The ratio of the number of chairs in the first row to the number of chairs in the second row to the number of chairs in the third row is 3 : 4 : 5. The second row has 20 chairs.Find (a) the total number of chairs in the class​

Answer 1

Topic :-

• Ratio

Given :-

• Some chairs are arranged in 3 rows in a class.
• Ratio of the number of chairs in the first row to the number of chairs in the second row to the number of chairs in the third row is 3 : 4 : 5.
• Second row has 20 chairs.

To Find :-

• Total number of chairs in the class.

Solution :-

Let us assume that :

First row contains 3x chairs.

Second row contains 4x chairs.

Third row contains 5x chairs.

3x : 4x : 5x : : 3 : 4 : 5, hence our assumption is correct.

It is given that second row has 20 chairs.

4x = 20 chairs

x = 20/4 chairs

x = 5 chairs

So,

Number of chairs in first row = 3x

Number of chairs in first row = 3 × (5 chairs)

Number of chairs in first row = 15 chairs

Number of chairs in third row = 5x

Number of chairs in third row = 5 × (5 chairs)

Number of chairs in third row = 25 chairs

Total number of chairs in class = Number of chairs in first row + Number of chairs in second row + Number of chairs in third row

Total number of chairs in class = 15 chairs + 20 chairs + 25 chairs

Total number of chairs in class = 60 chairs

Answer :-

• So, total number of chairs in the class is 60.