Question
There are black and white marbles in a jar in the ratio
4:5. After 20 marbles of each type are added, the ratio becomes 6:7. Find the original number of white marbles.Solution
ATQ,
Let the original number of black and white marbles be 4x and 5x.
ATQ:
(4x + 20)/(5x + 20) = 6/7
⇒ 7(4x + 20) = 6(5x + 20)
⇒ 28x + 140 = 30x + 120
⇒ 2x = 20
⇒ x = 10
Original white marbles = 5 × 10 = 50
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