In a single day, it rained for many hours. From 2pm to 4pm, it rained at a rate of 4 inches per hour. From 4pm to 7pm, it rained at a rate of 3 inches per hour. And from 7pm to 9pm, it rained at a rate of 0.5 inches per hour. If the rain gauge started out the day already containing 2 inches of rainwater, how many inches of water will the gauge contain at 9pm? Give the rationale and then the answer.
Let's think step by step. From 2pm to 4pm is 4 - 2 = 2 hours. Thus, from 2 - 4pm, raining at 4 inches per hour, it added 8 inches to the rain gauge. From 4pm to 7pm is 7 - 4 = 3 hours. Thus, from 4 - 7pm, raining at a rate of 3 inches per hour, it added 3 * 3 = 9 inches to the rain gauge. From 7pm to 9pm is 9 - 7 = 2 hours. Thus, from 7 - 9pm, raining at a rate of 0.5 inches per hour, it added 2 * 0.5 = 1 inch to the gauge. If the gauge originally contained 2 inches of water, by 9pm the gauge contained 2 + 8 + 9 + 1 = 20 inches of water.. The answer is: 20.

Cindy had 20 marbles which is 5 more than what Lisa had. If Cindy gave her 12 marbles, how many more marbles does Lisa have now? Give the rationale and then the answer.
Let's think step by step. Lisa had 20 - 5 = 15 marbles. Since Cindy gave 12 marbles, then she only has 20 - 12 = 8 marbles left. Since Lisa received 12 marbles, then Lisa has 15 + 12 = 27 marbles now. Hence, Lisa has 27 - 8 = 19 marbles more than Cindy.. The answer is: 19.

A rancher owns a mixture of 8 sheep and 5 cattle that graze on his land. In a typical year, the rancher will allow his animals to feed off his pastures for as long as possible before they run out of grass. After the pastures run out of grass, he must buy feed corn for $10 per bag. Each cow eats 2 acres of grass per month, and each sheep eats 1 acre of grass per month. Additionally, a bag of feed corn can feed each cow for 1 month and each sheep for 2 months.  If the rancher's pasture contains 144 acres of grass, how much will the rancher need to spend on feed corn to feed his animals each year? Give the rationale and then the answer.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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Let's think step by step. First, the 144 acres of grass will be eaten according to the equation 5 * 2 * T + 8 * 1 * T = 144. Solving this equation for T, we find 18 * T = 144, or T = 8 months of food are covered by the animals grazing on the rancher's pasture. This means the farmer must buy feed corn for the remaining 12 - 8 = 4 months. Next, the rancher's 8 sheep will require 4 / 2 = 2 bags of feed corn each, or 8 * 2 = 16 bags of feed corn in total for the 4 month period. The rancher's 5 cows will require 4 / 1 = 4 bags of feed corn each, or 5 * 4 = 20 bags of feed corn in total for the month. Therefore, the rancher needs 16 + 20 = 36 bags of feed corn for all of his animals. So, the rancher will need to spend 36 * 10 = $360 per year on feed corn.. The answer is: 360.