# Direct and inverse proportion class 8

## RATIO

The number of times one quantity contains another quantity of same kind is called the ‘RATIO’ of the two quantities. Clearly, the ratio of two quantities is equivalent to the fraction that one quantity is of the other.

Observe carefully that the two quantities must be of the same kind. There can be a ratio between Rs. 20 and Rs. 30 but cannot be between Rs. 20 and 30 mangoes.

Form of ratio = a → antecedent.

or a : b b  → consequent. fractions

Ratio is not altered by multiplying or dividing both its terms by the same number.

Thus 3 : 5 is the same as 6 : 10 and 15 : 20 is the same as 3 : 4.

### COMPOUND RATIO:

Ratio are compound when antecedent multiplied by antecedent and consequents multiplied by consequent.

If a : b, c : d, e : f

Then compound ratio is a x c x e/b x d x f

question 1. Find the ratio compounded if the four ratios 4 : 3, 9 : 13, 26 : 5 and 2 : 15.

Solution: The compound ratio = .

### DUPLICATE RATIO:

If a : b then a2 : b2 is duplicate ratio.

question 1. Find duplicate ratio of 4 : 3.

Solution: 42 : 32 = 16 : 9.

### TRIPLICATE RATIO:

If a : b, then a3 : b3 is triplicate ratio.

question 1. Find triplicate ratio of .

Solution:

### SUBDUPLICATE RATIO:

If a : b then is subduplicate ratio.

question 1. Find subduplicate ratio of 3 : 4 .

Solution:

### SUBTRIPLICATE RATIO:

If a : b then is subtriplicate.

question 1. Find the subtriplicate of 27 : 8.

Solution:

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