# 1.4 Multiply and divide integers  (Page 2/4)

 Page 2 / 4

Division follows the same rules as multiplication!

For division of two signed numbers, when the:

• signs are the same , the quotient is positive .
• signs are different , the quotient is negative .

And remember that we can always check the answer of a division problem by multiplying.

## Multiplication and division of signed numbers

For multiplication and division of two signed numbers:

• If the signs are the same, the result is positive.
• If the signs are different, the result is negative.
Same signs Result
Two positives
Two negatives
Positive
Positive
If the signs are the same, the result is positive.
Different signs Result
Positive and negative
Negative and positive
Negative
Negative
If the signs are different, the result is negative.

Divide: $-27÷3$ $-100÷\left(-4\right).$

## Solution

1. $\begin{array}{cccccc}& & & & & \hfill -27÷3\hfill \\ \begin{array}{c}\text{Divide, with different signs, the quotient is}\hfill \\ \text{negative.}\hfill \end{array}\hfill & & & & & \hfill -9\hfill \end{array}$

2. $\begin{array}{cccccc}& & & & & \hfill \phantom{\rule{0.3em}{0ex}}-100÷\left(-4\right)\hfill \\ \begin{array}{c}\text{Divide, with signs that are the same the}\hfill \\ \text{quotient is positive.}\hfill \end{array}\hfill & & & & & \hfill \phantom{\rule{0.3em}{0ex}}25\hfill \end{array}$

Divide: $-42÷6$ $-117÷\left(-3\right).$

$-7$ 39

Divide: $-63÷7$ $-115÷\left(-5\right).$

$-9$ 23

## Simplify expressions with integers

What happens when there are more than two numbers in an expression? The order of operations still applies when negatives are included. Remember My Dear Aunt Sally?

Let’s try some examples. We’ll simplify expressions that use all four operations with integers—addition, subtraction, multiplication, and division. Remember to follow the order of operations.

Simplify: $7\left(-2\right)+4\left(-7\right)-6.$

## Solution

$\begin{array}{cccccc}& & & & & \hfill 7\left(-2\right)+4\left(-7\right)-6\hfill \\ \text{Multiply first.}\hfill & & & & & \hfill -14+\left(-28\right)-6\hfill \\ \text{Add.}\hfill & & & & & \hfill -42-6\hfill \\ \text{Subtract.}\hfill & & & & & \hfill -48\hfill \end{array}$

Simplify: $8\left(-3\right)+5\left(-7\right)-4.$

$-63$

Simplify: $9\left(-3\right)+7\left(-8\right)-1.$

$-84$

Simplify: ${\left(-2\right)}^{4}$ $\text{−}{2}^{4}.$

## Solution

1. $\begin{array}{cccccc}& & & & & \hfill \phantom{\rule{5em}{0ex}}{\left(-2\right)}^{4}\hfill \\ \text{Write in expanded form.}\hfill & & & & & \hfill \phantom{\rule{5em}{0ex}}\left(-2\right)\left(-2\right)\left(-2\right)\left(-2\right)\hfill \\ \text{Multiply.}\hfill & & & & & \hfill \phantom{\rule{5em}{0ex}}4\left(-2\right)\left(-2\right)\hfill \\ \text{Multiply.}\hfill & & & & & \hfill \phantom{\rule{5em}{0ex}}-8\left(-2\right)\hfill \\ \text{Multiply.}\hfill & & & & & \hfill \phantom{\rule{5em}{0ex}}16\hfill \end{array}$

2. $\begin{array}{cccccc}& & & & & \hfill \text{−}{2}^{4}\hfill \\ \begin{array}{c}\text{Write in expanded form. We are asked}\hfill \\ \text{to find the opposite of}\phantom{\rule{0.2em}{0ex}}{2}^{4}.\hfill \end{array}\hfill & & & & & \hfill \text{−}\left(2·2·2·2\right)\hfill \\ \text{Multiply.}\hfill & & & & & \hfill \text{−}\left(4·2·2\right)\hfill \\ \text{Multiply.}\hfill & & & & & \hfill \text{−}\left(8·2\right)\hfill \\ \text{Multiply.}\hfill & & & & & \hfill -16\hfill \end{array}$

Notice the difference in parts and . In part , the exponent means to raise what is in the parentheses, the $\left(-2\right)$ to the ${4}^{\text{th}}$ power. In part , the exponent means to raise just the 2 to the ${4}^{\text{th}}$ power and then take the opposite.

Simplify: ${\left(-3\right)}^{4}$ $\text{−}{3}^{4}.$

81 $-81$

Simplify: ${\left(-7\right)}^{2}$ $\text{−}{7}^{2}.$

49 $-49$

The next example reminds us to simplify inside parentheses first.

Simplify: $12-3\left(9-12\right).$

## Solution

$\begin{array}{cccccc}& & & & & \hfill 12-3\left(9-12\right)\hfill \\ \text{Subtract in parentheses first.}\hfill & & & & & \hfill 12-3\left(-3\right)\hfill \\ \text{Multiply.}\hfill & & & & & \hfill 12-\left(-9\right)\hfill \\ \text{Subtract.}\hfill & & & & & \hfill 21\hfill \end{array}$

Simplify: $17-4\left(8-11\right).$

29

Simplify: $16-6\left(7-13\right).$

52

Simplify: $8\left(-9\right)÷{\left(-2\right)}^{3}.$

## Solution

$\begin{array}{cccccc}& & & & & \hfill 8\left(-9\right)÷{\left(-2\right)}^{3}\hfill \\ \text{Exponents first.}\hfill & & & & & \hfill 8\left(-9\right)÷\left(-8\right)\hfill \\ \text{Multiply.}\hfill & & & & & \hfill -72÷\left(-8\right)\hfill \\ \text{Divide.}\hfill & & & & & \hfill 9\hfill \end{array}$

Simplify: $12\left(-9\right)÷{\left(-3\right)}^{3}.$

4

Simplify: $18\left(-4\right)÷{\left(-2\right)}^{3}.$

9

Simplify: $-30÷2+\left(-3\right)\left(-7\right).$

## Solution

$\begin{array}{cccccc}& & & & & \hfill -30÷2+\left(-3\right)\left(-7\right)\hfill \\ \text{Multiply and divide left to right, so divide first.}\hfill & & & & & \hfill -15+\left(-3\right)\left(-7\right)\hfill \\ \text{Multiply.}\hfill & & & & & \hfill -15+21\hfill \\ \text{Add.}\hfill & & & & & \hfill 6\hfill \end{array}$

Simplify: $-27÷3+\left(-5\right)\left(-6\right).$

21

Simplify: $-32÷4+\left(-2\right)\left(-7\right).$

6

## Evaluate variable expressions with integers

Remember that to evaluate an expression means to substitute a number for the variable in the expression. Now we can use negative numbers as well as positive numbers.

When $n=-5,$ evaluate: $n+1$ $\text{−}n+1.$

## Solution

 Simplify. −4

 Simplify. Add. 6

When $n=-8,$ evaluate $n+2$ $\text{−}n+2.$

$-6$ 10

When $y=-9,$ evaluate $y+8$ $\text{−}y+8.$

$-1$ 17

Evaluate ${\left(x+y\right)}^{2}$ when $x=-18$ and $y=24.$

## Solution

 Add inside parenthesis. (6) 2 Simplify. 36

Evaluate ${\left(x+y\right)}^{2}$ when $x=-15$ and $y=29.$

196

Evaluate ${\left(x+y\right)}^{3}$ when $x=-8$ and $y=10.$

8

Evaluate $20-z$ when $z=12$ and $z=-12.$

## Solution

 Subtract. 8

 Subtract. 32

#### Questions & Answers

integer greater than 2 and less than 12
Emily Reply
2 < x < 12
Felix
I'm guessing you are doing inequalities...
Felix
Actually, translating words into algebraic expressions / equations...
Felix
hi
Darianna
hello
Mister
He charges $125 per job. His monthly expenses are$1,600. How many jobs must he work in order to make a profit of at least $2,400? Alicia Reply at least 20 Ayla what are the steps? Alicia 6.4 jobs Grahame 32 Grahame 1600+2400= total amount with expenses. 4000/125= number of jobs needed to make that min profit of 2400. answer is 32 Orlando He must work 32 jobs to make a profit POP what is algebra Azhar Reply repeated addition and subtraction of the order of operations. i love algebra I'm obsessed. Shemiah hi Krekar One-fourth of the candies in a bag of M&M’s are red. If there are 23 red candies, how many candies are in the bag? Leanna Reply they are 92 candies in the bag POP rectangular field solutions Navin Reply What is this? Donna t muqtaar the proudact of 3x^3-5×^2+3 and 2x^2+5x-4 in z7[x]/ is anas Reply ? 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? Manhwa Reply 44.19% Scott 40.22% Terence 44.2% Orlando I don't know Donna if you want the discounted price subtract$725 from $1299. then divide the answer by$1299. you get 0.4419... but as percent you get 44.19... but to the nearest tenth... round .19 to .2 and you get 44.2%
Orlando
you could also just divide $725/$1299 and then subtract it from 1. then you get the same answer.
Orlando
p mulripied-5 and add 30 to it
Tausif Reply
p mulripied-5 and add30
Tausif
p mulripied-5 and addto30
Tausif
how
muqtaar
Can you explain further
Monica Reply
p mulripied-5 and add to 30
Tausif
-5p+30?
Corey
p=-5+30
Jacob
How do you find divisible numbers without a calculator?
Jacob Reply
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?
Ariana Reply
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?
Kirisma Reply
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
No; 65m/hr
albert
hello, I have algebra phobia. Subtracting negative numbers always seem to get me confused.
Alicia Reply
what do you need help in?
Felix
subtracting a negative....is adding!!
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
Niazmohammad
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
hi
albert
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
John Reply
168.50=R
Heather
john is 5years older than wanjiru.the sum of their years is27years.what is the age of each
achol Reply
46
mustee
j 17 w 11
Joseph
john is 16. wanjiru is 11.
Felix
27-5=22 22÷2=11 11+5=16
Joyce

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