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At a Glance - Decimals in Use

Paychecks and Expenses

Sample Problem

Luis works 2.5 hours a day, 4 days a week. How many hours a week does Luis work?

2.5 hours/day × 4 days/week = 10 hours/week

Only 10 hours a week? Guess who will not be jumping into a roomful of money? Luis.

Prices and Counting Change

Sample Problem

Nathan buys a sandwich for $6.50. It's one of those "gourmet" sandwiches, which just means that it's a regular turkey sandwich but comes with a packet of dijon mustard. Anyway, he pays with a $10 bill. Assuming the cashier doesn't screw things up, how much change does Nathan get?

$10 – $6.50 = $3.50

So Nathan gets $3.50 in change.


Sample Problem

Kate and Jim ate at a restaurant. The total bill was $56.80. They want to leave only a 10% tip because their server spilled two drinks and one plate of nachos into their laps. How much of a tip should they leave?

By the way, there's a really quick way to figure out 10% of a bill: just move the decimal point one spot to the left. Kate and Jim's bill was $56.80, so they can slide that decimal point over between the 5 and 6 to get $5.68. That's only if they're leaving a measly 10% tip though, which we really don't recommend doing. Restaurant servers have bills to pay too, y'know?

Sharing Work

Sample Problem

A librarian has 50 books that need to go back on the shelves. She has her five student helpers divide up the books evenly. How many books will each student put back on the shelves?

 books each

Hopefully they're not all enormous bricks like War and Peace.

Exercise 1

Alfred works 40 hours per week at $7.25 per hour, the federal minimum wage. How much money does Alfred make per week?

Exercise 2

Karen drives a car to work every day. Whenever she stops for gas she puts 10 gallons in the tank. If gas costs $2.49/gallon (apparently Karen is still living in 2009) and she has to fill the tank twice a week, how much money per week does she spend on gas?

Exercise 3

Jenny doesn't eat breakfast, but she spends five dollars a day on lunch and ten dollars a day on dinner. How much money does Jenny spend on food in a week? And what does she have against the most important meal of the day?

Exercise 4

Alison buys a $17.99 CD with a $20 bill. How much change does she get?

Exercise 5

Mary bought a pair of shoes for $34.50 and a pair of socks for $10.19. If she paid with a $50 bill, how much change should she get?

Exercise 6

Zachary got $200 for his birthday. He bought a $50 stereo, 4 CDs at $9.99 each, and a 6-pack of root beer for $5.60. He put the rest in the bank. (Man, good taste in soda and he's saving for his future? Get him while he's single, ladies.) How much did Zachary put in the bank?

Exercise 7

How much will it cost to buy 5 candy bars at $0.99 each?

Exercise 8

How much will it cost to buy 5 books at $6.95 each? (A "book," FYI, was this contraption made out of paper that people used to read before the Internet came along.)

Exercise 9

How much will it cost to buy 11 cookies at 97 cents each?

Exercise 10

Alice left a 10% tip on her bill of $14.50. How much of a tip did she leave?

Exercise 11

How do you quickly figure out how much 10% of your bill is?

Exercise 12

How do you quickly figure out how much 20% of your bill is?

Exercise 13

Thomas left a 20% tip on his bill of $17. How much tip did he leave?

Exercise 14

How much is a 15% tip on a bill of $17?

Exercise 15

A classroom of students is assigned a 152-page book to read. Four of the students decide they will each read a fourth of the book and then tell each other about it. Really, guys? With only 152 pages? You should just be glad you don't have a teacher who's obsessed with Anna Karenina. Anyway, how many pages must each devious student read?

Exercise 16

There are 51 chairs in an auditorium, and three students have been assigned to put away the chairs. How many chairs must each student put away?

Exercise 17

Alyssa has four cookies but five friends who want to try some. Alyssa decides to eat them all herself. Then, realizing this wouldn't make a very challenging math problem, she has a change of heart and decides to divide the cookies equally between her friends and herself. How much of a cookie does each person get?

Exercise 18

Gabe has eaten a few cookies, but he still has nine left and his stomach is starting to grumble, so he decides to lay off them. If he shares these equally among six of his friends, how many cookies does each person get?

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