NCERT Class 8 Mathematics Solutions: Chapter 13 – Direct and Inverse Proportions Exercise 13.1 Part 1

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1. Following are the car parking charges near a railway station up to:

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hours,

hours,

hours,

hours,

Check if the parking charges are in direct proportion to the parking time.

Answer:

Charges per hour:

So, the charges per hour are not same, i.e.,

So, the parking charges are not in direct proportion to the parking time.

2. A mixture of paint is prepared by mixing part of red pigments with parts of base. In the following table, find the parts of base that need to be added.

Answer:

The ratio of parts of red pigment and parts of base be

When

When

When

3. In Question above, if part of a red pigment requires of base, how much red pigment should we mix with of base?

Answer:

Consider,

The parts of red pigment mix with base be

Since it is in direct proportion.

parts

So, with base parts red pigment should be mixed.

4. A machine in a soft drink factory fills bottles in six hours. How many bottles will it fill in five hours?

Answer:

Consider,

The number of bottles filled in five hours be .

Here ratio of hours and bottles are in direct proportion

bottles

So, machine will fill bottles in five hours.