A bag contains red, blue, and green balls in the ratio 3 : 5 : 7. If there are 45 blue balls, how many total balls are there in the bag?

Question: A bag contains red, blue, and green balls in the ratio 3 : 5 : 7. If there are 45 blue balls, how many total balls are there in the bag?

Solution: Given ratio = Red : Blue : Green = 3 : 5 : 7
Let the numbers be:
Red = 3x, Blue = 5x, Green = 7x

Given:
5x = 45
⇒ x = 45 ÷ 5 = 9

Now calculate total balls:
= 3x + 5x + 7x
= (3 + 5 + 7)x = 15x
= 15 × 9 = 135