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UKMT Junior Mathematical Olympiad, 2017

Algebra Difficulty 3.0 AMC 10/12 Prove it United Kingdom

A jar contains red and white marbles in the ratio 1 : 4. When Jenny replaces 2 of the white marbles with 7 red marbles, the ratio becomes 2 : 3. What is the ratio of the total number of marbles in the jar now to the total number in the jar before?

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