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?
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
