Question

A bag contains 35 red counters only. Chen adds green counters to the bag. The probability of picking a green counter is now 0.3 How many green counters did Chen add?

Answer 1

15

Explanation:

Red counters = 35

Number of green counters = x

P(picking a green counter) = 0.3

Probability = required outcome / Total possible outcomes

Required outcome = number of green counter

Total possible outcomes = green counter + red counter

Hence,

0.3 = x / (35+x)

0.3(35 + x) = x

10.5 + 0.3x = x

10.5 = x - 0.3x

10.5 = 0.7x

x = 10.5 / 0.7

= 15

Number of green counters = 15