Multiple choice

The ratio of white balls and black balls in a container is 8 : 5. If 10 white balls are taken out from the container and 15 new black balls are added in the container, the ratio of white balls and black balls will be 3 : 4. How many white balls were there in the container initially?

  1. 35

  2. 37

  3. 40

  4. 42

  5. 45
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Initial ratio 8x:5x. (8x - 10) / (5x + 15) = 3/4. 32x - 40 = 15x + 45. 17x = 85, x = 5. White balls = 8 * 5 = 40.

AI explanation

Let the initial number of white balls be 8x and black balls be 5x. After removing 10 white balls and adding 15 black balls, the new amounts are (8x minus 10) and (5x plus 15). Setting the new ratio to 3/4 gives 4(8x minus 10) = 3(5x plus 15), which simplifies to 17x = 85, meaning x equals 5. The initial number of white balls was 8 times 5, which equals 40.

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