A bag contains 8 red balls and x blue balls, the odd against drawing a blue ball are 2: 5. What is the value of x? (Ans:20)
Ans: No. of blue balls be x
No. of red balls be 8
Total no. of balls = x + 8
Probability of drawing blue balls = x/8 + x
Probability of drawing red balls = 8/8 + x
8/8 + x : x/8 + x = 2 : 5
2 (x/8 + x) = 5 ( 8/8 + x )
2x = 40
∴ x = 20