Question

Two positive numbers X and Y are inversely proportional. if X increases by 20% then percentage decreases in y is a) 15 b) 16 2/3 c) 17 11/9 d) 25

Answer 1

Little bit mistake while typing option , The correct answer will be 200/3 .

Solution :-

We know that for every inversely proportional numbers, the given product of the number will be constant always, when all given conditions are same.

Let x and y = 20 both.

Here xy is = Constant

20 × 20 = Constant

If x increases by 20%, then the new value of x will be 24.

Therefore the product of x and y will be 480.

But we should know that the product of x and y should constant like 400 in this case.

Then y must be decrease to maintain the product constant.

x × y = 400

24y = 400

y= 400/24

y = 50/3

And in the terms of percentage.

= $\frac{(20 - 50/3)}{20} * 400$

= 1/6 × 400

= 200/3 .

Hence the percentage decreased in y will be 200/3 .