[Question]: Angela has half as many insects as Jacob does, and Jacob has 5 times as many insects as Dean. If Dean has 30 insects, how much does Angela have?
[Answer]: Jacob has 5 * 30 = 150 insects. So, Angela has 150 / 2 = 75 insects.
So the answer is 75.

[Question]: Tim buys a book of esoteric words. He learns 10 words from it a day. In 2 years the book has increased the number of words he knows by 50%. How many words did he know originally?
[Answer]: In 2 years there are 365 * 2 = 730 days. So he has learned 730 * 10 = 7300 words. He knew 1 / .5 = 2 times that number of words before the book. So he knew 7300 * 2 = 14600 words before.
So the answer is 14600.

[Question]: Olaf is sailing across the ocean with 25 men, including himself. He needs 1/2 a gallon of water per day per man. The boat can go 200 miles per day and he needs to travel 4,000 miles. How many gallons of water does he need?
[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.
user
He needs 12.5 gallons per day because 25 x .5 = 12.5. It will take 20 days of travel because 4,000 / 200 = 20. He will need 250 gallons of water because 20 x 12.5 = 250.
So the answer is 250.