Q: Julian has 80 Facebook friends. 60% are boys and 40% are girls. Boyd has twice as many friends who are girls and has 100 friends total. What percentage of Boyd’s friends are boys?
A: 36
Step-by-step reasoning process: Julian's number of friends who are girls is .40 * 80 = 32. Boyd has twice as many friends as Julian who are girls, a total of 2 * 32 = 64. If Boyd has 100 friends, he has 100 - 64 = 36 boys. The percentage of boys in Boyd's Facebook friends is 36 / 100 * 100 = 36.


Q: The lifespan of a hamster is 6 years less than that of a bat. The lifespan of a frog is 4 times that of a hamster. Altogether, the lifespan of the animals is 30 years. What is the lifespan of the bat?
A: 10
Step-by-step reasoning process: Let’s set up an equation by calling the lifespan of a bat x, and therefore the lifespan of the hamster x – 6, and the lifespan of the frog 4 (x – 6) which add together to equal 30, like this: x + x – 6 + 4 (x – 6) = 30. That gives us 6x – 30 = 30 and we should add 30 to each side to try to isolate the x. Now we have 6x = 60, which we will divide by 6, 6x / 6 = 60 / 6. This gives us x = 10. The bat has a lifespan of 10 years.


Q: James earns $20 an hour while working at his main job. He earns 20% less while working his second job. He works 30 hours at his main job and half that much at his second job. How much does he earn per week?
A: 840
Step-by-step reasoning process: James earns 20 * .2 = $4 less while working his second job. So he earns 20 - 4 = $16 an hour. At his first job he earns 20 * 30 = $600. He works 30 / 2 = 15 hours at his second job. So he earns 15 * 16 = $240. So he earns 600 + 240 = $840 a week.


Q: Jerry needs to shingle 3 roofs. Each roof is made of two slanted rectangular sides measuring 20 feet by 40 feet. If he needs 8 shingles to cover one square foot of roof, how many shingles does he need total?
A: 38400

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
Step-by-step reasoning process: First find the area of one side of a roof: 20 feet * 40 feet = 800 square feet. Then multiply that number by 2 to find the total area of both sides of the roof: 800 square feet / side * 2 sides = 1600 square feet. Then multiply that number by the number of roofs to find the total area of all the roofs: 1600 square feet / roof * 3 roofs = 4800 square feet. Then multiply the total area of the roofs by the number of shingles needed per square foot to find the total number of shingles needed: 4800 square feet * 8 singles / square foot = 38400 shingles.