Emery and Serena go to their school library, and each borrows a copy of The life of Jack Steve's book to read for their school project. If Emery can read five times as fast as Serena, and the book takes her 20 days to read, what's the average number of days the two take to read the book?

If Emery took twenty days to read the book, then it took Serena 5*20 =

<<20*5=100>>100 days to read the whole book. The total number of days taken by the two to read the book is 100+20 = <<100+20=120>>120 days. The average number of days the two take to read the book is 120/2 = <<120/2=60>>60 days. #### 60 A laboratory has 22 beakers of liquid in a fume hood, and 8 of the beakers have copper ions in them. Adding three drops of a solution will turn the liquid in a beaker blue if there are copper ions present. If the beakers are tested one by one for copper ions and 45 drops are used before all 8 beakers with copper ions are found, how many beakers without copper ions were tested? There were 45 / 3 = <<45/3=15>>15 beakers tested to find all the beakers with copper ions. Thus, 15 - 8 = <<15-8=7>>7 beakers without copper ions were tested. #### 7 Jolene and Phil have four children, each with the same birthday. They gave birth to their first child exactly 15 years ago. They gave birth to their second child exactly one year after the birth of their first child. They gave birth to their third child on the fourth birthday of their second child. Two years after the birth of their third child, they gave birth to their fourth child. How old, in years, is their fourth child? Their 1st child was born 15 years ago, and therefore is <<15=15>>15 years old. Their 2nd child was born 1 year after their 15-year-old child, and therefore is 15-1=<<15-1=14>>14 years old. Their 3rd child was born 4 years after their 14-year-old child, and therefore is 14-4=10 years old. Their 4th child was born 2 years after their 10-year-old child, and therefore is 10-2=8 years old. #### 8 Bryan starts exercising at home during quarantine. To start, he decides to do 3 sets of 15 push-ups each. Near the end of the third set, he gets tired and does 5 fewer push-ups. How many push-ups did he do in total? In total, Bryan would have done 3 sets * 15 push-ups/set = <<3*15=45>>45 push-ups. Subtracting the push-ups he didn't do in the third set, Bryan did 45 push-ups - 5 push-ups = <<45-5=40>>40 push-ups. #### 40 Mark buys a loaf of bread for $4.20 and some cheese for $2.05. He gives the cashier $7.00. If the cashier only has 1 quarter and 1 dime in his till, plus a bunch of nickels, how many nickels does Mark get in his change? First subtract the cost of Mark's groceries from the amount he gives the cashier to find how much he gets in change: $7.00 - $4.20 - $2.05 = $<<7-4.2-2.05=0.75>>0.75 Then subtract the value of a quarter in cents (25) and the value of a dime in cents (10) from the change amount to find how much Mark gets paid in nickels: $0.75 - $0.25 - $0.10 = $<<0.75-0.25-0.10=0.40>>0.40 Now divide the amount Mark gets in nickels by the value per nickel in cents (5) to find how many nickels Mark gets: $0.40 / $0.05/nickel = <<0.40/0.05=8>>8 nickels #### 8 Max likes to collect model trains. He asks for one for every birthday of his, and asks for two each Christmas. Max always gets the gifts he asks for, and asks for these same gifts every year for 5 years. At the end of the 5 years, his parents give him double the number of trains he already has. How many trains does Max have now? Max gets 1+2=<<1+2=3>>3 trains per year. He repeats this for 5 years, meaning he gets 5*3 =<<5*3=15>>15 trains. When this number is doubled by his parents, it becomes 15*2= <<15*2=30>>30 trains. Since he already had 15 model trains, his total becomes 15+30= <<15+30=45>>45 trains. #### 45 Jake has $5000. He spends $2800 on a new motorcycle, and then spends half of what's left on a concert ticket. Jake then loses a fourth of what he has left. How much money does he have left? Jake has 5000-2800 = $<<5000-2800=2200>>2200 left Jake has 2200/2 = $<<2200/2=1100>>1100 Jake loses 1100/4 = $<<1100/4=275>>275 Jake has 1100-275 = $<<1100-275=825>>825 left. #### 825 In April, Tank gathered 10 more Easter eggs than Emma in their first round of egg hunt. However, Emma gathered twice as many eggs as Tank in their second round of egg hunt, while Tank's total number of eggs in the second round was 20 less than the number she had gathered in the first round. If the total number of eggs in the pile they were collecting with 6 other people was 400 eggs, and Emma gathered 60 eggs in the second egg hunt round, find the number of eggs that the 6 other egg hunters collected? Tank's total number of eggs in the second round was 60/2=<<60/2=30>>30 since Emma gathered twice as many eggs as Tank in their second round of egg hunt. The total number of eggs that Emma and Tank gathered in the second round was 60+30=<<60+30=90>>90 Tank's total number of eggs in the second round was 20 less than the number she had gathered in the first round, meaning she had gathered 30+20=<<30+20=50>>50 eggs in the first round of egg hunt. Tank gathered 10 more Easter eggs than Emma in their first round of egg hunt, meaning Emma collected 50-10=40 eggs The total number of eggs Emma and Tank collected in the first round was 40+50=<<40+50=90>>90 In the two rounds, Emma and Tank gathered 90+90=<<90+90=180>>180 eggs If the total number of eggs in the pile they were collecting with 6 other people was 400 eggs, the six other people gathered 400-180=<<400-180=220>>220 eggs #### 220 Jack is running a bake sale to help pay for his basketball team's uniforms. He's already sold 4 brownies for $3 each and 5 lemon squares for $2 each. If Jack's goal is to make $50 and he sells cookies for $4 each, how many cookies does he need to sell to reach his goal? Jack earned from the brownies $3 per brownie * 4 brownies = $<<3*4=12>>12. Jack earned from the lemon squares $2 per square * 5 squares = $<<2*5=10>>10. He still needs to earn $50 - $12 - $10 = $<<50-12-10=28>>28. He sells cookies for $4 each, so Jack still needs to sell $28 / $4 = <<28/4=7>>7 cookies. #### 7 Frank has 7 one-dollar bills, 4 five-dollar bills, 2 ten-dollar bills, and 1 twenty-dollar bill. He goes to buy peanuts, which cost $3 a pound. He buys what he wants and has $4 in change. He plans to eat the peanuts all in one week. How many pounds does he eat on average per day? Frank has $7 in one dollar bills because 7 x 1 = <<7*1=7>>7 Frank has $20 in five dollar bills because 4 x 5 = <<20=20>>20 Frank has $20 in ten dollar bills because 2 x 10 = <<2*10=20>>20 Frank has 67 dollars in total because 7 + 20 + 20 + 20 = <<7+20+20+20=67>>67 Frank spent $63 because 67 - 4 = <<67-4=63>>63 Frank bought 21 pounds of peanuts because 63 / 3 = <<63/3=21>>21 He eats 3 pounds a day on average because 21 / 7 = <<21/7=3>>3 #### 3