Question

An urn contains 12 red balls, 15 yellow balls and 18 blue balls. A ball is choosen at random, then to find the probability of choosing a blue and red coloured balls, fill in the boxes.

Total number of balls = 12 + `square` + `square` = `square`

(1) Let E be the event that the choosen ball is blue.

Number of blue balls = `square`

Thus, 

P(E) = `"Number of blue balls"/"Total number of balls"`

= `square/square`

(2) Let F be the event that the choosen ball is red.

Number of red balls = `square`

Thus,

P(F) = `square/"Total number of balls"`

= `square/square`

Answer 1

Total number of balls = 12 + 15 + 18 = 45

(1) Let E be the event that the choosen ball is blue.

Number of blue balls = 18

Thus, 

P(E) = `"Number of blue balls"/"Total number of balls"`

= `bb18/bb45`

(2) Let F be the event that the choosen ball is red.

Number of red balls = 12

Thus,

P(F) = `bb("Number of red balls")/"Total number of balls"`

= `bb12/bb45`