Question

There is a bag with only red marbles and blue marbles.The probability of randomly choosing a red marble is 7/8.There are 56 marbles in total in the bag and each is equally likely to be chosen.Work out how many red marbles there must be.

Answer 1

Therefore the number red marble in the bag is 49.

Explanation:

Probability: The ratio of favorable out comes to the total outcomes.

`P=\frac{\textrm{Favorable outcomes}}{\textrm{Total outcomes}}`

Given that the probability of choosing of a red marble is
`\frac78` . There are 56 marbles in the bag.

Consider the number of marble be x.

Therefore, the probability of choosing of red marble is

`=\frac{\textrm{The number of red marble}}{\textrm{Total number of marble}}`

`=(x)/(56)`

According to the problem,

`(x)/(56)=(7)/(8)`

`\Rightarrow x=\frac78 * 56`

`\Rightarrow x=49`

Therefore the number red marble in the bag is 49.