cat 2021 Question 7

Question

A box has 450 balls, each either white or black, there being as many metallic white balls as metallic black balls. If 40% of the white balls and 50% of the black balls are metallic, then the number of non-metallic balls in the box is

Accepted Answer

Let the number of white balls be x and black balls be y

So we get x+y =450 (1)

Now metallic black balls = 0.5y

Metallic white balls = 0.4x

From condition 0.4x=0.5y

we get 4x-5y=0 (2)

Solving (1) and (2) we get

x=250 and y =200

Now number of Non Metallic balls = 0.6x+0.5y = 150+100 = 250

Question 7.

Question Explanation