Paperback, 160-208 pages.
Awards:
Recommended by TD Monthly, NSTA Recommends: National Parenting Publications Award, Best Books Award ;NCTM Recommends
Math is a critical part of our everyday lives. The second title in the award-winning "101 Things Everyone Should Know" series helps you understand how you use math dozens of times--every day. With entertaining, real-life connections in sports, travel, food, hobbies and more, math concepts are simplified and explained. You'll even learn some fun trivia and math history! Using an engaging question-and-answer format, 101 Things Everyone Should Know About Math is perfect for kids, parents, educators, and anyone interested in the difference between an Olympic event score of 9.0 and a Richter scale score of 9.0.
Sample Questions!
1.There and Back Again
Zach lives a mile from school. It takes him 15 minutes to ride his bike to school, but only 5 minutes to ride home (There's a lesson on motivation here, but that's beside the point). What is Zach's average speed?
A. 4 miles per hour
B. 6 miles per hour
C. 8 miles per hour
D. 12 miles per hour
2.Team Player
Daniel plays soccer on a team in the local BES ("Busy Every Saturday") soccer league. There are 10 players on his team. At any one time, eight players are on the field. The coach always chooses his players randomly. What percent of the time does Daniel not play?
3.Triple Doubles
In Monopoly, you roll two dice and move the number of spaces equal to the sum of the dice. If you roll doubles, you get to roll again. However, if you roll 3 doubles in a
row, you go directly to jail, do not pass Go and do not collect $200. What are the chances of this happening?
a) 1 in 6 c) 1 in 216
b) 1 in 36 d) 1 in a million
4.Super Sprinter
World-class sprinter Allyson Fleetfeet can run the 100-meter dash in about 10 seconds. If Allyson could maintain that pace for an entire marathon (26 miles and 385 yards), about how long would it her take to finish?
a) around 10 minutes c) around 3 hours
b) around 1 hour d) around 6 hours
Anwers
1. The answer is: B, 6 miles per hour
Distance is given in miles, and we want to know Zach's rate in miles per hour, or miles/hour. If it takes Zach 15 minutes to go one mile to school and 5 minutes to come home, it takes Zach a total of 20 minutes to go 2 miles. That means Zach's average rate is: r = 2 miles/20 minutes = 2 miles/(1/3) hour = 6 miles per hour.
2. The answer is: 20%.
An easy way to calculate this is to note that, all things being equal, two of the 10 players will be sitting out at any given time, so everyone will sit 2/10 (or 20%) of the time. Another way to solve this problem is to figure out how many different combinations of players can be fielded-and then determine how many include Daniel. Choosing at random, there are 10 players that the coach can pick for the first person to sit out, and nine choices remaining for the second person to sit out. That would be 90 choices for players to sit out. However, it doesn't matter whether a player is picked first or second to sit out. To take that into account, we need to divide by the number of ways two players can be chosen (2). Therefore, we get 90/2 = 45 possible ways for two players to sit on the bench. Next, we need to figure out how many of those ways include Daniel. There are nine combinations of Daniel and one other player sitting out. So out of 45 possible choices, 9 include Daniel. 9/45 reduces to 1/5, or 20%.
3. The answer is: C, 1 in 216
NEED A CLUE? First, determine the chances of rolling doubles on the first roll.
There are six outcomes possible for each die, making a total of 36 possible outcomes. There are six ways to roll doubles (1-1, 2-2, 3-3, 4-4, 5-5, and 6-6). Six in 36 is the same as 1/6. The same holds true on the second and third rolls. Since the rolls don't influence each other (the dice have no recollection of what was rolled each time), we need to multiply the results of each separate roll together. When we do, we get: 1/6 x 1/6 x 1/6 = 1/216 , or 1 in 216.
4. The answer is: B, around 1 hour
- First, convert Allyson's speed to kilometers per second: 100m/10sec x 1km/1000m = 0.01 km/s.
- To estimate the length of the marathon in kilometers, we toss out the 385 yards and get the equation 26mi x 1km/.6mi = 26 x 1/0.6 km.
- Now the problem becomes "What is 1/0.6?" Well, 1/0.5 is 2 and 1/0.67 is 1.5 so 1/0.6 must be somewhere in between.
- Using what we know, we find that 26/0.5 = 52 and 26/0.67 = 39. We know the answer is in the middle there somewhere, so let's pick 45 km (because it is easy to work with).
- To get the time it will take to run the marathon, we need to divide the distance by the rate in the units (km/s). The formula is 45km/(0.01km/s), or 45km/(0.01km/s)= 4500 seconds.
- We can convert 4,500 seconds to hours by dividing by 3,600 (60 minutes x 60 seconds = 3,600 seconds in an hour).
- The answer is 4,500/3,600 = 5/4 = 1.25 hours
As it turns out, it's impossible to sprint for that long. World-class marathoners take between 2 and 2.25 hours to finish a race.
These aren't your ordinary mysteries! One Minute Mysteries: 65 Short Mysteries You Solve With Math! challenges readers of all ages to become super sleuths. These fun mysteries are each one minute long and have a unique twist-you need to tap into your mathematical wisdom to solve them. Plus, they will help you figure out the greatest mystery of all: why you actually need the skills you learn in math class! Written by the same father-daughter team who brought you the award-winning One Minute Mysteries: 65 Short Mysteries You Solve With Science!, this entertaining and educational book is easy to use at home, in school, or in the car. This book is the perfect solution for any kid, parent, or educator who loves good mysteries, good math, or both!
Sample Questions and Answers!
1. Heavy Toll
"A speeding ticket? What?" Suzy's father said as he opened the day's mail. "What's the matter, Daddy?" Suzy asked. "Well, Suzy, this ticket says that we were speeding on the toll road we took when we were driving back from the state science fair last weekend," he explained. As drivers entered the road they got a receipt showing the time and exit number. The exit numbers were also mileage markers. When they got off the road, drivers had to pay different amounts depending on how far they went. "Are you sure they're right?" Suzy asked. "What does it say?" "Well, it says that we got on at exit 64 at 12:13 p.m., then got off the road at exit 148 at 1:33 p.m.," he said. "And it says the speed limit was 55 miles an hour-I thought it was 65. How can they know if we were speeding?" he asked. "I didn't see any police cars." "It's too bad, but they're right," Suzy said. "How do you know?" he asked.
Answer: "If we got on the road at 12:13 and got off at 1:33, that means we were on the road for one hour and 20 minutes, or 80 minutes," Suzy explained. "Since the exit numbers are mileage markers, the distance between exits 64 and 148 is 84 miles-148 minus 64. That means we went 84 miles in 80 minutes-that's more than one mile per minute, which is more than 60 miles per hour. So we were speeding, since the speed limit was 55 miles per hour." "To figure it out exactly," she added, "84 miles divided by 80 minutes makes 1.05 miles per minute. Multiplying 1.05 miles per minute by 60 minutes in an hour to get miles per hour means we averaged 63 miles per hour." "Well, we were going less than that for some of the time," her father said.
"Yes, but to average 63 miles an hour, we must have been going faster than that at other times," she said. "I hope that ticket isn't too expensive."
2. Pancake Mix-up
"Mooommm!" Meg yelled from the kitchen. "Can you please come down here?" Meg's family and two other families had rented a house at a ski resort for a long weekend. Each family was going to cook and clean up for one of the three days. It was the morning of Meg's family's day. While Meg's mother finished getting dressed, Meg went into the kitchen and started preparing the pancake mix. They had brought individual-sized serving packages of mix. They also had several boxes of cereal and bread to make toast, but everyone had said they wanted pancakes. "I'll be there in a minute, Meg. What's the problem?" her mother called. "I have everything ready to make the pancakes. But each of these packages needs two-thirds of a cup of milk, and there's no two-thirds measuring cup in this kitchen," Meg called. "All they have is a three-fourths measuring cup. Can I just estimate?"
"Not if you want the pancakes to be any good," her mother replied. "Never mind," Meg said a moment later. "I have the solution." "What did you do?" her mother asked as she walked into the kitchen.
Answer: "I did some math. It's a question of least common multiples," Meg told her mother. "First, I figured out how many times you'd have to fill each kind of measure to reach a whole number. With the three-fourths measuring cup, to reach a whole number you'd need to use the measure four times. Four times three-fourths is twelve-fourths, which reduces to three. So filling that measure four times gives us three cups of milk. "Each package of mix required two-thirds of a cup of milk. If we had a two-thirds measuring cup, you would need to fill it three times to get a whole number. Three times two-thirds is six-thirds, which reduces to two. So, filling a two-third measuring cup three times would give us two cups of milk," she continued. "All I had to do then was find the least common multiple of three and two-the smallest number that is a multiple of both. That's six. Since I would need to fill the three-fourths measuring cup four times to get three cups, I would need to fill it twice that many times, eight times, to get six cups. I did that and put the milk in the bowl. And since three fillings of a two-thirds measuring cup would give us two cups, to get six cups I would need three times that many, or nine, to get the right amount of mix. So I added nine packages of the mix. I hope everyone's hungry!"
3. Cover Up
As a birthday present to her little sister Laura, Miranda had promised to paint the inside of the family playhouse for her.
Years before, their father had painted the walls and floor pink, Miranda's favorite color. But since Laura was the one who mainly used it now, and her favorite color was blue, she wanted the pink covered up. Miranda measured the inside of the playhouse. The two longer sides were 10 feet long and 6 feet high, and the ends were 6 feet long and 6 feet high. Above that was the inside of the roof, which didn't need to be painted. Her father warned her that covering up the pink would require two coats of paint. Later at the hardware store, Laura chose a shade of blue that she liked. "Okay, here's a can that says it will cover 520 square feet," Miranda said. "Each longer side of the playhouse is 60 square feet-10 times 6-so together they would be twice that, or 120 square feet. The ends are 36 square feet each-6 times 6-so together they would be twice that, or 72 square feet. And 120 plus 72 is 192 square feet. Painting that twice means I need to cover 384 square feet in total-two times 192. So a can that covers 520 square feet will be enough." Since she was paying for it out of her own money, Miranda didn't want to buy too much. "That's enough to cover the walls, but don't forget you have to paint the floor, too," her father said. "Oops! I didn't measure the floor," Miranda said. "Should we drive back home to measure it?" Laura asked. "Or should you just buy an extra can of paint to be sure you have enough?"
Answer: "Neither," Miranda said. "Since we know the two longer sides of the playhouse are 10 feet long and the ends are 6 feet long, the floor must be a 6 foot by 10 foot rectangle, meaning its area is 60 square feet. Painting that twice means I have to cover another 120 square feet. So I need to cover 504 square feet-384 plus 120-in total. That means one can will still be enough."
8. Go Take a Hike
Carla and Amanda's family was vacationing at a national park one summer and decided to take a hike down from the top of a gorge to see the river below. A sign said: Three trails lead from here to different points along the river.
The trails do not join each other, and each takes approximately two hours to walk. Riverside Trail: Steepest. Plan on taking 30 minutes down, 1 1/2 hours back. Scenic Overlook Trail: Medium steepness. Plan on taking 40 minutes down, 1 hour 20 minutes back. Forest Path: Most level. Plan on taking 1 hour down, 1 hour back. Caution: No water available on the trails. Do not drink water from the river or any streams along the way. Please carry water and use it wisely. They saw another family that had just finished a hike. "How was it?" Carla asked. "It was great," the other family's mother said. "But take that warning about water seriously. We'd used one-third of our water when we got to the bottom, and that was just right." "What trail did you take?" Amanda asked.
Answer: "They took the Scenic Overlook Trail," Carla said. "The Forest Path takes the same amount of time to walk back as to walk down-one hour each way. When you reach the bottom of that trail, you've walked one half of the total-one hour out of two hours. The Riverside Trail takes three times as long to walk back as to walk down-90 minutes back versus 30 minutes down. When you reach the bottom of that trail, you've walked one quarter of the total-30 minutes out of 120. The Scenic Overlook Trail takes twice as long to walk back as to walk down-80 minutes back versus 40 minutes down. So when you reach the bottom of that trail, you've walked for one third of the total-40 minutes out of 120."
Ages 11-15.
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