The ratio of Red Balls to Blue Balls is 3:7. 70% of the Red balls and 30% of the Blue balls are tennis balls. How many of the balls are tennis balls?  Options:
A) 44 % B) 40 % C) 45 % D) 42 % E) 48 %

Rationale: let total no of balls 100 , red ball 30 and blue ball 70 , so tennis ball for red and blue ball respectively 30 * 70 / 100 = 21 and 70 * 30 / 100 = 21 so total 42 tennis balls out of 100 balls . . so required % is 42 % answer : d
Answer: D