IBPS SO Prelims Exam Model Paper 8

Given:
Total number of ball = 30
Number of red and white balls = 18
Formula used:
P(E) =

Number‌of‌favourable‌outcomes

Total‌number‌of‌outcomes

Calculation:
Let 'E' is the probability of the event.
⇒ Number of white and red balls = 18
⇒ Total number of balls = 30
⇒ Number of blue balls = 30 – 18
⇒ 12
⇒ Number of favourable outcomes = 12C1 × 18C1
⇒ [

(12×11!)

(1!×11!)

] × [

(18×17!)

(1!×17!)

]
⇒ 12 × 18
⇒ Total number of outcomes = 30C2
⇒ [

(30×29×28!)

(2!×28!)

]
⇒ 15 × 29
⇒ P(E) =

(12×18)

(15×29)

⇒

72

145