General Rules
(+) x (+) =
(+) or positive
-12 x -3
36
-14/-2
7
Describe and correct the error.
2/3*(-3/4)=1/2
The answer should be negative because a positive times a negative is a negative.
(+) x (-) =
-
64 x (-4)
-256
864/-16
-54
Describe and correct the error.
-3/8-:-4/5=-15/32
The answer should be positive because a negative divided by a negative is a positive.
Tell whether the expression is positive or negative without evaluating.
-3/10 * (-8/15)
positive
-4.4 x (-6.02)
26.488
-78/5
-15 3/5
The temperature in NYC decreased at a constant rate from 15°F to -15°F in 3 hours. How many degrees did the temperature decrease by per hour?
10 degrees per hour
How is multiplying and dividing rational numbers similar to multiplying and dividing integers?
The same rules for signs of integers are applied to rational numbers.
-9.4 x (-4.7)
44.18
-1 5/6-:4 1/6
-11/25
A cable on a fishing boat lowers a fish trap into a lake at a rate of 5 feet per second. What is the change in depth of the fish trap after 15 seconds?
-75 feet
Tell whether the expression is positive or negative without evaluating.
-6/5-:(-1/2)*6.3*(-0.6)-:2/3*7 7/8-:100
negative
(-4/5)(15/8)(7/3)(-1)
7/2. = 3 1/2
Write -5 4/6 as a decimal.
-5.6 (6 repeating)
An elevator goes from the 136th floor to the 10th floor of a skyscraper in 30 seconds. The elevator travels at a constant speed.
What is the elevator's rate of change in floors per second?
-4.2 floors/second