RULES FOR MULTIPLYING AND DIVIDING NEGATIVE NUMBERS

Evaluate the following :

Problem 1 :

-5 x 8 x 5

Solution :

= -5 x 8 x 5

To multiply these three numbers, first we have to multiply any two numbers and then the answer can be multiplied by another digit.

= -40 x 5

= -200

So, the answer is -200.

Problem 2 :

-7 x 3 x (-3)

Solution :

= -7 x 3 x (-3)

Multiplying -7 and 3, we get -21

= -21 x (-3)

= 63

So, the answer is 63.

Problem 3 :

-2 x 5 x -2

Solution :

-2 x 5 x -2

Multiplying -2 and 5, we get -10

= -10 x (-2)

= 20

So, the answer is 20.

Problem 4 :

(-3)³

Solution :

= (-3)³

Since the power is 3, we have to multiply the base three times.

= -3 x (-3) x (-3)

 = -27

So, the answer is -27.

Problem 5 :

-8 x 5 x -5

Solution :

= -8 x 5 x -5

By multiplying -8 and 5, we get -40

= -40 x -5

= 200

So, the answer is

Problem 6 :

(-2)²

Solution :

= (-2)²

Since the power is 2, we have to repeat the base two times.

= -2 x (-2)

= 4

So, the answer is 4.

Problem 7 :

-2 x 9 x (-5)

Solution :

= -2 x 9 x (-5)

Multiplying -2 and 9, we get -18.

= -18 x (-5)

= 90

So, the answer is 90.

Problem 8 :

A skydiver falls 70 meters per second for 4 seconds. How many meters does he fall ?

Solution :

Number of meter falls = 70 meter

Number of seconds it is travelling = 4

The distance it is covering = 4(70)

= 280 meters

Problem 9 :

When Tania bought a new cycle for $540, she borrowed the money from her parents. She repays them $70 per week for 6 weeks. How much does Tania still owe her parents ?

Solution :

Cost of new cycle = $540

Amount she pays for every week = $70

Number of weeks she is paying = 6

Amount she has to still owe = 540 - 6(70)

= 540 - 420

= 120

Problem 10 :

Roger's business has $12500 in the bank. He must pay each of his 8 employees a wage of $389 per week for 4 weeks. How much money will be remaining in the bank ?

Solution :

Number of persons to get salary = 8

Amount for salary per week = $389

Number of weeks salary to be paid = 4

Remaining amount = 12500 - 4 x 8(389)

= 12500 - 32(389)

= 12500 - 12448

= $52

So, $52 is the remaining amount.

Problem 11 :

In a mathematics competition, students are awarded 3 points for a right answer and penalised 4 points for a wrong answer. Amy gave 6 wrong answer and 24 right answers. Sean gave 14 wrong answers and 16 right answers.

a) How many points did each student score ?

b) By how many points did Amy beat sean ?

Solution :

Number of points for right answer = 3

Number of points for wrong answers = 4

About Amy :

Number of questions answered correctly = 24

Number of questions answered incorrectly = 6

About Sean :

Number of questions answered correctly = 16

Number of questions answered incorrectly = 14

a)

Amy's score = 24 (3) - 6 (4)

= 72 - 24

= 48

Sean's score = 16(3) - 14(4)

= 48 - 56

= -8

b) 

= 48 - (-8)

= 56 points