Question

A bag contains 4 white balls and some red balls. If the probability of drawing a white ball from the bag is 2/5, find the number of red balls in the bag.

Answer 1

let the number of red ball be x.
total number of red balls = 4+x.
probability of drawing a white ball is 2/5.
therefore:
44+x=252(4+x)=4*54+x=2*5=10x=10−4x=6
thus the number of red balls are 6.

Answer 2

Answer:

The number of red balls are 6.

Step-by-step explanation:

Given a bag contains 4 white balls and some red balls. If the probability of drawing a white ball from the bag is 2/5,

we have to find the number of red balls in the bag.

Let the number of red balls be x.

Given number of white balls = 4

Total number of balls = 4+x.

$\text{Probability of drawing a white ball is }\frac{4}{4+x}$

As given

$\text{Probability of drawing a white ball is }\frac{2}{5}$

∴ $\frac{4}{4+x}=\frac{2}{5}$

⇒ $20=2(4+x)$

⇒ $4+x=10$

⇒ $x=6$

Hence, number of red balls are 6.