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Three-part ratio changes after adding or removing amounts: find an unknown

This type of question, asked 3 times: 12 Sep 2025 S2, 15 Sep 2025 S1, 26 Sep 2025 S2. All 3 questions below, oldest first.

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  1. Question 1

    12 Sep 2025 S2

    52
    The number of red, blue, and green marbles in a bag is in the ratio 3:4:63 : 4 : 6. If 20 red marbles, 15 blue marbles, and an unknown number of green marbles are added to the bag, the ratio of red, blue, and green marbles becomes 4:5:74 : 5 : 7. Determine the number of green marbles added.

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  2. Question 2

    15 Sep 2025 S1

    55
    A container holds a mixture of three liquids A, B, and C in ratio 2 : 3 : 5. If 6 liters of liquid A, 12 liters of liquid B, and a certain amount of liquid C are added to the container, the new ratio of liquids A, B, and C becomes 3 : 5 : 8. Find the quantity (in liters) of liquid C added.

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  3. Question 3

    26 Sep 2025 S2

    60
    A bag contains red, blue, and green balls in the ratio 4:5:64 : 5 : 6. If 6 red balls are removed and 3 green balls are added, the new ratio becomes 2:5:72 : 5 : 7. How many red balls were originally in the bag?

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