Algebra 1 : How to multiply integers

Study concepts, example questions & explanations for Algebra 1

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Example Questions

Example Question #1 : How To Multiply Integers

Evaluate 5x + 3y when x = 7 and y = 9.

Possible Answers:

66

–62

62

–66

8

Correct answer:

62

Explanation:

Plug in 7 for x and 5 for y, giving you 5(7) + 3(9). This is equal to 35 + 27, which equals 62.

5x + 3y

5(7) + 3(9)

35 + 27 = 62

Example Question #2 : How To Multiply Integers

A plane flies at a rate of 210mi/h. If the plane has flown for five hours, how many miles has it traveled?

Possible Answers:

1050mi

840mi

215mi

42mi

1000mi

Correct answer:

1050mi

Explanation:

Multiply the rate of travel (210 mi/hr) by the time traveled (5 hours), and you get the total distance, 1050 miles.

distance = rate * time

distance = (210mi/hr)(5hr)

distance = 1050mi

Example Question #2 : How To Multiply Integers

Find the volume of a cube that is five feet on each side.

Possible Answers:

125ft3

10ft3

5ft3

25ft3

15ft3

Correct answer:

125ft3

Explanation:

To find the volume of a cube, you cube the side length, raising it to the thrid power. 5 cubed is 125.

(5ft)3 = 5ft*5ft*5ft = 125ft3

Example Question #3 : How To Multiply Integers

What is the square root of 81? 

Possible Answers:

9

40.5

–9

27

3

Correct answer:

9

Explanation:

9 * 9 = 81, and thus 9 is the square root of 81. It is true that (–9) * (–9) = 81, but it is a convention that "the square root" refers to the positive value.  Had the question asked for "a square root" or "the square roots" of 81, –9 would be acceptable.

Example Question #3 : How To Multiply Integers

What is (–16) * (–2)? 

Possible Answers:

32

–32

–8

64

8

Correct answer:

32

Explanation:

When multiplying two negative numbers, the negatives cancel each other out, leaving a positive solution, thus, we can think of (–16)(–2) as (16)(2), which is 32.

(–16) * (–2)

(–1)(16) * (–1)(2)

(–1)(–1) * (16)(2)

(1) * (16)(2)

16 * 2

32

Example Question #2 : How To Multiply Integers

Solve:

\(\displaystyle \frac{(3\cdot 7-4)}{2\cdot 4^3}\)

Possible Answers:

\(\displaystyle \frac{9}{128}\)

\(\displaystyle 0.13\)

\(\displaystyle 7.5\)

None of the available answers

\(\displaystyle \frac{17}{128}\)

Correct answer:

\(\displaystyle \frac{17}{128}\)

Explanation:

\(\displaystyle \frac{(3\cdot 7-4)}{2\cdot 4^3}\)

\(\displaystyle \frac{(3\cdot 7-4)}{2\cdot 64}\)

\(\displaystyle \frac{(21-4)}{128}\)

\(\displaystyle \frac{17}{128}\)

 

Example Question #4 : How To Multiply Integers

If \(\displaystyle p\) is an integer, which of the following must be odd?

Possible Answers:

\(\displaystyle 3p+1\)

\(\displaystyle p-1\)

\(\displaystyle 7p\)

\(\displaystyle 2p+1\)

\(\displaystyle 3p\)

Correct answer:

\(\displaystyle 2p+1\)

Explanation:

While all of the answers could result in an odd answer, only \(\displaystyle 2p+1\) guarantees an odd answer.  Since any integer multiplied by 2 is even, adding 1 will always give the next consecutive odd integer.

Example Question #1 : How To Multiply Integers

What is \(\displaystyle (9) * (-7)\) ?

Possible Answers:

\(\displaystyle -56\)

\(\displaystyle 2\)

\(\displaystyle -16\)

\(\displaystyle -63\)

\(\displaystyle 63\)

Correct answer:

\(\displaystyle -63\)

Explanation:

Multiply the absolute values to get the magnitude of the answer.

\(\displaystyle 9*7=63\)

Remember the following rules:

Positive * negative = negative

Positive * positive = positive

Negative * negative = positive

Since we are dealing with a positive and a negative, our answer will be negative.

\(\displaystyle 9*-7=-63\)

Example Question #4 : How To Multiply Integers

\(\displaystyle 100-30\times4+25\times 2= ?\)

Possible Answers:

\(\displaystyle 610\)

\(\displaystyle 10\)

\(\displaystyle 230\)

\(\displaystyle 90\)

\(\displaystyle 30\)

Correct answer:

\(\displaystyle 30\)

Explanation:

\(\displaystyle \textup{Order of operations: Perform multiplication functions before addition/subtraction.}\)

\(\displaystyle 100-30\times4+25\times 2= \;\;100-120+50\;\;\;= \;\;\;30\)

Example Question #2 : How To Multiply Integers

\(\displaystyle \frac{\left ( 2-4 \right )^{3}}{3\times 6}=\)

Possible Answers:

\(\displaystyle -\frac{4}{9}\)

\(\displaystyle \frac{4}{9}\)

\(\displaystyle -\frac{9}{4}\)

\(\displaystyle \frac{9}{4}\)

Correct answer:

\(\displaystyle -\frac{4}{9}\)

Explanation:

\(\displaystyle \frac{\left ( 2-4^ \right )^{3}}{3\times 6}= \frac{-2^{3}}{18}=\frac{-8}{18}=\frac{4}{9}\)

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