Question: There are 25 different layers of rock in a canyon's strata. Five of the layers are limestone. Half of the rest are sandstone. Four of the remaining are quartz. Half of the rest are shale. The rest are all different kinds of rock. How many kinds of rock make up only one layer in the canyon's strata?
Answer: There are 25 - 5 = 20 layers of rock that are not limestone. Half of those 20 are sandstone, so there are 20 / 2 = 10 that are not limestone or sandstone. Four of those are quartz, so 10 - 4 = 6 layers are not limestone, sandstone, or quartz. Half of the rest are shale, so 6 / 2 = 3 kinds of rock remain that make up only one layer in the strata. The answer is 3.

Question: Bill and Joan both work for a library. 5 years ago, Joan had 3 times as much experience as Bill. Now she has twice as much experience as Bill. How many years of experience does Bill have now?
Answer: Let b be Bill's years of experience and j be Joan's years of experience. We know that j - 5 = 3(b - 5) and j = 2b. Substituting the second equation into the first equation, we get 2b - 5 = 3(b - 5). Multiplying through the parentheses, we get 2b - 5 = 3b - 15. Adding 15 to both sides, we get 2b + 10 = 3b. Subtracting 2b from both sides, we get 10 = b. The answer is 10.

Question: Every 2 years, the number of swans at Rita's pond doubles. Currently, there are 15 swans in the pond. How many swans will there be in ten years?
Answer: If currently there are 15 swans in the pond, in two years' time there will be 15 * 2 = 30 swans. In another two years, the number of swans in the pond will double to 2 * 30 = 60 swans. In another two years, the number of swans in the pond will double to 2 * 60 = 120 swans. If after 6 years there are 120 swans in the pond, in eight years times there will be 2 * 120 = 240 swans. In another two years, which is 10 years, there will be 2 * 240 = 480 swans in the pond. The answer is 480.

Question: Kylie has 34 stamps in her collection. Her friend, Nelly, has 44 more stamps than Kylie. How many stamps do Kylie and Nelly have together?
Answer:
Nelly has 34 + 44 = 78 stamps. Thus, Kylie and Nelly have 34 + 78 = 112 stamps. The answer is 112.