A box has 120 pencils in red, blue, and black in the ratio 2 : 3 : 5. If 10 red and 20 black pencils are removed, what is the new ratio of red to black pencils?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 7 : 20.
Red : Blue : Black = 2 : 3 : 5
Tota = 2k + 3k + 5k = 10k = 120
⇒ k = 120/10 = 12
Red = 2 × 12 = 24, Blue = 3 × 12 = 36, Black = 5 × 12 = 60
Remove 10 red, 20 black ⇒ Red = 24 - 10 = 14, Black = 60 - 20 = 40
New ratio of red and black pencils = 14 : 40 = 7 : 20