Direct Proportion: Two quantities are said to be directly proportional, if on the increase (or decrease) of the one, the other increases (or decreases) to the same extent.
Eg. Cost is directly proportional to the number of articles.

Indirect Proportion: Two quantities are said to be indirectly proportional, if on the increase of the one, the other decreases to the same extent and vice-versa.
Eg. The time taken by a car to cover a certain distance is inversely proportional to the speed of the car.

Note: In solving problems by chain rule, we compare every item with the term to be found out.

SAMPLE PROBLEMS

1. Running at the same constant rate, 6 identical machines can produce a total of 270 bottles per minute. At this rate, how many bottles could 10 such machines produce in 4 minutes?

a. 648
b. 1800
c. 2700
d. 10800

2. In a diary farm, 20 cows eat 20 bags in 20 days. In how many days one cow will eat one bag of husk?

a. 10 Day
b. 1/10 Day
c. 20 Day
d. 40 Day

3. A flagstaff 17.5 m high casts a shadow of length 40.25 m. The height of the building, which casts a shadow of length 28.75 m under similar conditions will be:

a. 10M
b. 12.5M
c. 17.5M
d. 21.25M

4. If 8 men can reap 40 hectares in 12 days, then how many hectares can 30 men reap in 20 days?

a. 175 hectares
b. 225 hectares
c. 250 hectares
d .275 hectares

Answer Key:

1. B
2. C
3. B
4. C