Question

There is a bag filled with 3 blue and 5 red marbles.

A marble is taken at random from the bag, the colour is noted and then it is not replaced.
Another marble is taken at random.
What is the probability of getting 2 of the same colour?



JUST NEED THE ANSWER IN A FRACTION PLEASE

Answer 1

`(13)/(28)`

Explanation:

Given:

Blue marbles: 3

Reb marbles: 5

Total marbles: 8

Two marbles are selected at random, one after the other with replacement.

Getting the same colour of marbles from the selection means the two marbles are both red or both blue.

(a) Probability of getting 2 marbles being red in colour

i. Probability of picking a red at the first selection:

Number of red marbles ÷ Total number of marbles

=> 5 ÷ 8 =
`(5)/(8)`

ii. Probability of picking a red at the second selection:

Number of remaining red marbles ÷ Total number of remaining marbles

Since after the first pick, the marble is not replaced, the remaining red marbles is 4 while the total number of remaining marbles is 7

=> 4 ÷ 7 =
`(4)/(7)`

iii. The probability of getting both marbles being red is the product of i and ii above. i.e

`(5)/(8)` x
`(4)/(7)` =
`(5)/(14)`

(b) Probability of getting 2 marbles being blue in colour

i. Probability of picking a blue at the first selection:

Number of blue marbles ÷ Total number of marbles

=> 3 ÷ 8 =
`(3)/(8)`

ii. Probability of picking a blue at the second selection:

Number of remaining blue marbles ÷ Total number of remaining marbles

Since after the first pick, the marble is not replaced, the remaining blue marbles is 2 while the total number of remaining marbles is 7

=> 2 ÷ 7 =
`(2)/(7)`

iii. The probability of getting both marbles being blue is the product of i and ii above. i.e

`(3)/(8)` x
`(2)/(7)` =
`(3)/(28)`

(c) Probability of getting 2 marbles of the same colour.

The probability of getting 2 marbles of same colour is the sum of the probability of getting both marbles of red colour and the probability of getting both marbles as blue colour. i.e The sum of a(iii) and b(iii)

`(5)/(14)` +
`(3)/(28)` =
`(13)/(28)`

The probability of getting 2 of the same colour is
`(13)/(28)`