# 1.10 Systems of measurement  (Page 2/13)

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## Make unit conversions.

1. Multiply the measurement to be converted by 1; write 1 as a fraction relating the units given and the units needed.
2. Multiply.
3. Simplify the fraction.
4. Simplify.

When we use the identity property of multiplication to convert units, we need to make sure the units we want to change from will divide out. Usually this means we want the conversion fraction to have those units in the denominator.

Ndula, an elephant at the San Diego Safari Park, weighs almost 3.2 tons. Convert her weight to pounds.

## Solution

We will convert 3.2 tons into pounds. We will use the identity property of multiplication, writing 1 as the fraction $\frac{2000\phantom{\rule{0.2em}{0ex}}\text{pounds}}{1\phantom{\rule{0.2em}{0ex}}\text{ton}}.$

 $\text{3.2 tons}$ Multiply the measurement to be converted, by 1. $\text{3.2 tons}\cdot 1$ Write 1 as a fraction relating tons and pounds. $\text{3.2 tons}\cdot \frac{\text{2,000 pounds}}{\text{1 ton}}$ Simplify. Multiply. $\text{6,400 pounds}$ Ndula weighs almost 6,400 pounds.

Arnold’s SUV weighs about 4.3 tons. Convert the weight to pounds.

8,600 pounds

The Carnival Destiny cruise ship weighs 51,000 tons. Convert the weight to pounds.

102,000,000 pounds

Sometimes, to convert from one unit to another, we may need to use several other units in between, so we will need to multiply several fractions.

Juliet is going with her family to their summer home. She will be away from her boyfriend for 9 weeks. Convert the time to minutes.

## Solution

To convert weeks into minutes we will convert weeks into days, days into hours, and then hours into minutes. To do this we will multiply by conversion factors of 1.

 9 weeks Write $1$ as $\frac{\text{7 days}}{\text{1 week}}$ , $\frac{\text{24 hours}}{\text{1 day}}$ , and $\frac{\text{60 minutes}}{\text{1 hour}}$ . $\frac{\text{9 wk}}{1}\cdot \frac{\text{7 days}}{\text{1 wk}}\cdot \frac{\text{24 hr}}{\text{1 day}}\cdot \frac{\text{60 min}}{\text{1 hr}}$ Divide out the common units. Multiply. $\frac{9\cdot 7\cdot 24\cdot \text{60 min}}{1\cdot 1\cdot 1\cdot 1}$ Multiply. $\text{90,720 min}$

Juliet and her boyfriend will be apart for 90,720 minutes (although it may seem like an eternity!).

The distance between the earth and the moon is about 250,000 miles. Convert this length to yards.

440,000,000 yards

The astronauts of Expedition 28 on the International Space Station spend 15 weeks in space. Convert the time to minutes.

151,200 minutes

How many ounces are in 1 gallon?

## Solution

We will convert gallons to ounces by multiplying by several conversion factors. Refer to [link] .

 1 gallon Multiply the measurement to be converted by 1. $\frac{\text{1 gallon}}{1}\cdot \frac{\text{4 quarts}}{\text{1 gallon}}\cdot \frac{\text{2 pints}}{\text{1 quart}}\cdot \frac{\text{2 cups}}{\text{1 pint}}\cdot \frac{\text{8 ounces}}{\text{1 cup}}$ Use conversion factors to get to the right unit. Simplify. Multiply. $\frac{1\cdot 4\cdot 2\cdot 2\cdot \text{8 ounces}}{1\cdot 1\cdot 1\cdot 1\cdot 1}$ Simplify. $\text{128 ounces}$ There are 128 ounces in a gallon.

How many cups are in 1 gallon?

16 cups

How many teaspoons are in 1 cup?

48 teaspoons

## Use mixed units of measurement in the u.s. system

We often use mixed units of measurement in everyday situations. Suppose Joe is 5 feet 10 inches tall, stays at work for 7 hours and 45 minutes, and then eats a 1 pound 2 ounce steak for dinner—all these measurements have mixed units.

Performing arithmetic operations on measurements with mixed units of measures requires care. Be sure to add or subtract like units!

Seymour bought three steaks for a barbecue. Their weights were 14 ounces, 1 pound 2 ounces and 1 pound 6 ounces. How many total pounds of steak did he buy?

## Solution

We will add the weights of the steaks to find the total weight of the steaks.

 Add the ounces. Then add the pounds. Convert 22 ounces to pounds and ounces. $\phantom{\rule{0.35em}{0ex}}$ 2 pounds + 1 pound, 6 ounces Add the pounds. $\phantom{\rule{0.35em}{0ex}}$ 3 pounds, 6 ounces Seymour bought 3 pounds 6 ounces of steak.

the proudact of 3x^3-5×^2+3 and 2x^2+5x-4 in z7[x]/ is
?
Choli
a rock is thrown directly upward with an initial velocity of 96feet per second from a cliff 190 feet above a beach. The hight of tha rock above the beach after t second is given by the equation h=_16t^2+96t+190
Usman
Stella bought a dinette set on sale for $725. The original price was$1,299. To the nearest tenth of a percent, what was the rate of discount?
44.19%
Scott
40.22%
Terence
44.2%
Orlando
p mulripied-5 and add 30 to it
Tausif
Tausif
Can you explain further
p mulripied-5 and add to 30
Tausif
How do you find divisible numbers without a calculator?
TAKE OFF THE LAST DIGIT AND MULTIPLY IT 9. SUBTRACT IT THE DIGITS YOU HAVE LEFT. IF THE ANSWER DIVIDES BY 13(OR IS ZERO), THEN YOUR ORIGINAL NUMBER WILL ALSO DIVIDE BY 13!IS DIVISIBLE BY 13
BAINAMA
When she graduates college, Linda will owe $43,000 in student loans. The interest rate on the federal loans is 4.5% and the rate on the private bank loans is 2%. The total interest she owes for one year was$1,585. What is the amount of each loan?
Sean took the bus from Seattle to Boise, a distance of 506 miles. If the trip took 7 2/3 hours, what was the speed of the bus?
66miles/hour
snigdha
How did you work it out?
Esther
s=mi/hr 2/3~0.67 s=506mi/7.67hr = ~66 mi/hr
Orlando
hello, I have algebra phobia. Subtracting negative numbers always seem to get me confused.
what do you need help in?
Felix
Heather
look at the numbers if they have different signs, it's like subtracting....but you keep the sign of the largest number...
Felix
for example.... -19 + 7.... different signs...subtract.... 12 keep the sign of the "largest" number 19 is bigger than 7.... 19 has the negative sign... Therefore, -12 is your answer...
Felix
—12
Thanks Felix.l also get confused with signs.
Esther
Thank you for this
Shatey
ty
Graham
think about it like you lost $19 (-19), then found$7(+7). Totally you lost just $12 (-12) Annushka I used to struggle a lot with negative numbers and math in general what I typically do is look at it in terms of money I have -$5 in my account I then take out 5 more dollars how much do I have in my account well-\$10 ... I also for a long time would draw it out on a number line to visualize it
Meg
practicing with smaller numbers to understand then working with larger numbers helps too and the song/rhyme same sign add and keep opposite signs subtract keep the sign of the bigger # then you'll be exact
Meg
Bruce drives his car for his job. The equation R=0.575m+42 models the relation between the amount in dollars, R, that he is reimbursed and the number of miles, m, he drives in one day. Find the amount Bruce is reimbursed on a day when he drives 220 miles
168.50=R
Heather
john is 5years older than wanjiru.the sum of their years is27years.what is the age of each
46
mustee
j 17 w 11
Joseph
john is 16. wanjiru is 11.
Felix
27-5=22 22÷2=11 11+5=16
Joyce
I don't see where the answers are.
Ed
Cindy and Richard leave their dorm in Charleston at the same time. Cindy rides her bicycle north at a speed of 18 miles per hour. Richard rides his bicycle south at a speed of 14 miles per hour. How long will it take them to be 96 miles apart?
3
Christopher
18t+14t=96 32t=96 32/96 3
Christopher
show that a^n-b^2n is divisible by a-b
What does 3 times your weight right now
Use algebra to combine 39×5 and the half sum of travel of 59+30
Cherokee
What is the segment of 13? Explain
Cherokee
my weight is 49. So 3 times is 147
Cherokee
kg to lbs you goin to convert 2.2 or one if the same unit your going to time your body weight by 3. example if my body weight is 210lb. what would be my weight if I was 3 times as much in kg. that's you do 210 x3 = 630lb. then 630 x 2.2= .... hope this helps
tyler
How to convert grams to pounds?
paul
What is the lcm of 340
Yes
Cherokee By OpenStax By Stephen Voron By Stephen Voron By By OpenStax By OpenStax By David Corey By Saylor Foundation By Mackenzie Wilcox By OpenStax