Question: One of the activities in Grade 6 PE class is to get the average weight of the students from each group. In one of the groups, the average weight of five girls is 45 kg while the average weight of five boys is 55 kg. What is the average weight of the ten students from that group?
Answer with step-by-step thinking: The sum of the weights of the five girls is 45 kg x 5 = 225 kg. The sum of the weights of the five boys is 55 kg x 5 = 275 kg. The sum of the weights of the ten students is 225 kg + 275 kg = 500 kg. Hence, the average weight of those ten students is 500 kg / 10 = 50 kg.
So the answer is 50.

Question: Sarah is checking out books from the library to read on vacation. She can read 40 words per minute. The books she is checking out have 100 words per page and are 80 pages long. She will be reading for 20 hours. How many books should she check out?
Answer with step-by-step thinking: Each book has 8,000 words because 100 x 80 = 8,000. She can finish each book in 200 minutes because 8,000 / 40 = 200. She will be reading for 1,200 minutes because 20 x 60 = 1,200. She needs to check out 6 books because 1,200 / 200 = 6.
So the answer is 6.

Question: Mary used 15 gallons of fuel this week. Last week she used 20% less. How much fuel did she use in total for the two weeks?
Answer with step-by-step thinking:
Last week, she used 15 gallons * 0.2 = 3 gallons less fuel than she used this week. This means that she used 15 gallons 3 gallons = 12 gallons of fuel last week. In total, Mary used 15 gallons + 12 gallons = 27 gallons of fuel.
So the answer is 27.