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E:\Working\Focus_Learning\Math_Genius-8\Open_Files\16_Chapter_12\Chapter_12
\ 06-Jan-2025 Surendra Prajapati Proof-7 Reader’s Sign _______________________ Date __________

1. Do you know why the photographer gave 20 copies of stamp-sized photos instead of 8 copies
of passport-sized photos for `60? Explain.

2. Find the ratio between the rates of per copy of a postcard-sized photo and a passport-sized
photo.
3. How many times a postcard-size photo is larger than a stamp-size photo?

4. Are the sizes of photos and their rates per copy proportional? Complete the table and discuss
your answer.
Photos Passport Postcard Stamp

Size (in sq. cm)
Rate per copy (in `)

Variation

In our daily life, we come across many situations where one thing depends on another thing(s).
For example, parking charges depend upon the number of hours the car is parked, the quantity of
coffee to prepare depends upon the number of persons, and the time taken to reach the destination
depends upon the speed of the train, etc.

Observe the following tables and think if both quantities increase or decrease in the same direction
or if one increases (or decreases) when the other decreases (or increases).

Table A

Quantity of CNG used (in kg) 1 2 5 8 15 10
Distance covered (in km) 12 24 60 96 180 120

Table B

Number of tickets booked for a show 3 2 6 9 20 15

Cost of tickets (in `) 1500 1000 3000 4500 10000 7500
Table C

Number of workers employed 4 6 12 3 5 10

Days required to build a house 45 30 15 60 36 18

Looking at the values given in the above tables, we can say that:
When two quantities are related to each other in such a way that the value of one quantity depends
upon the corresponding change of the other quantity, then the two quantities are said to be in
variation.
There are two types of variation:

1. Direct variation
2. Inverse or indirect variation

279 Direct and Indirect Variations