Question

50 balls are number 1 to 50 and a red dot is painted on those balls that are a multiple of 7. The balls are mixed into a bag and one ball is randomly chosen. What is the probability that the ball is numbered with a multiple of 5 or has a red dot?

Answer 1

Hello,

The multiples of 7 are 7,14,21,28,35,42,49 : 7 balls
The multiples of 5 are 5,10,15,20,25,30,35,40,45,50 :10 balls
In total there are 50 balls
But there is a commun ball 35

p=(7+10-1)/50=16/50=8/25=0.32