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:

Car are given in image

Car Are Given in Image

Car are given in image

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.

In the Table Parts of Red Pigment and Parts of Base
In the table parts of red pigment and parts of base

Parts of red pigment

1

4

7

12

20

Parts of base

8

___

____

___

__

Answer:

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

When

When

When

Parts of Red Pigment and Parts of Base
Parts of red pigment and parts of base

Parts of red pigment

1

4

7

12

20

Parts of base

8

32

56

96

160

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

Comparing Red Pigment and Base
Comparing red pigment and base to find unknown

Parts of red pigment

Parts of base

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 .

In Given Table Bottles and Hours
In given table bottles and hours

Hours

Bottles

x

Here ratio of hours and bottles are in direct proportion

bottles

So, machine will fill bottles in five hours.