Alfred works 40 hours per week at $7.25 per hour, the federal minimum wage. How much money does Alfred make per week?
Answer
40 × $7.25 = $290 per week
It ain't much, but he's still got his buddy Luis coming to him for a loan.
Example 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?
Answer
(cost per gallon) × (number of gallons) × (number of times per week) =
$2.49 × 10 × 2 = $49.80
Example 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?
Answer
(cost of food per day) × (days per week) =
($5 + $10) × 7 = $15 × 7 = $105
Or we can work it out this way instead:
(cost of lunch per week) + (cost of dinner per week) =
($5 × 7) + ($10 × 7) = $35 + $70 = $105
As for Jenny's aversion to breakfast, we can only assume she must have had some scarring run-in with a bacon strip as a young child.
Example 4
Alison buys a $17.99 CD with a $20 bill. How much change does she get?
Answer
$20 – $17.99 = $2.01
Example 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?
Answer
$50 – ($34.50 + $10.19) = $5.31
Example 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?
Answer
$200 – $50 – (4 × $9.99) – $5.60 = $104.44
To figure out the
total cost of 4 CDs at $9.99 each, we don't actually have to multiply
$9.99 by 4. That's too much work. Instead, we can round and then adjust
our figure later on to be more exact. Trust us—this will save you
valuable CD-buying time in the long run.
We know $9.99 is almost exactly
$10, so the 4 CDs cost about $40 total. However, this estimate is $0.01
(one cent) too high for each CD. Since there are 4 CDs, the estimate is 4
cents too high. Instead of $40, the CDs cost $39.96. Well, golly gee,
that sounds a whole lot cheaper than $40! What marketing genius came up
with that idea? He should get a raise!
Example 7
How much will it cost to buy 5 candy bars at $0.99 each?
Answer
We can round up and estimate the total price as 5 × $1.00 = $5. This estimate is 1 cent too high for each book, so subtract 5 × $0.01, or $0.05, from the estimate. Final answer is 5 – $0.05 = $4.95.
Or we can just multiply $0.99 × 5 = $4.95. Either way is cool.
Example 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.)
Answer
Our estimate is 5 × $7 = $35. This estimate is 5 cents too high for each
book, so subtract 5 × $0.05 = $0.25 from the estimate. Final answer is
$35 – $0.25 = $34.75.
Or we can do it the old-fashioned way: 5 × $6.95 = $34.75.
Example 9
How much will it cost to buy 11 cookies at 97 cents each?
Answer
11 × $0.97 = $10.67
Example 10
Alice left a 10% tip on her bill of $14.50. How much of a tip did she leave?
Answer
Example 11
How do you quickly figure out how much 10% of your bill is?
Answer
Move the decimal place one space to the left.
Example 12
How do you quickly figure out how much 20% of your bill is?
Answer
Move the decimal place one space to the left, then multiply by 2.
Example 13
Thomas left a 20% tip on his bill of $17. How much tip did he leave?
Answer
If we slide our decimal point over, we can see that 10% is $1.70. Then multiply by 2 to get $3.40. Hopefully his server won't be annoyed by those 40 pennies he left.
Example 14
How much is a 15% tip on a bill of $17?
Answer
15% × 17 = 0.15 × 17 = $2.55
Example 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?
Answer
Example 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?
Answer
Example 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?
Answer
Example 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?
Answer
Gabe gets 0, while the others each get 9 ÷ 6 = 1.5 cookies.
