Question 22. Identical balls have been placed in five identical test tubes as shown. Then, water is added to each of these test tubes. The water level in test tubes 1, 2, and 3 is the same. The water level in test tubes 4 and 5 is also the same, and twice as high as in the first three test tubes. Then, all balls are removed. Which test tube has the least water? Let's begin this problem by looking at test tubes 1, 2, and 3. Since the water level is the same, but the amount of balls is different. With this information, if we take out all the balls in all of the three test tubes, then we know that test tube 3 will have the least amount of water, since it has an equal water height when there are three balls, as the other test tubes do when they have two and one balls in them. So we can cross out 1 and 2. We can use the same logic for test tubes 4 and 5. Their water level is the same, but they have a different amount of balls. If we took out all of the balls in both of the test tubes, test tube 5 would have less water, so we can cross out test tube 4. Finally, we are left with test tubes 3 and 5. The water level of number 5 is twice as high as number 3. However, there are also twice as many balls. Using the same logic that we've been using before, but also realizing that there is twice the water level height in 5, if we removed all balls from test tube 3 and 5, we would see that test tube number 3 has less water. So the answer is C, 3.

test tubes

water level

ball count

least water

removal

identical balls

water levels

water analysis