True or False
12-8 = 4
True or False?
True
7 - (+ 9)
Are we moving to the left or right of the number line?
Left
Rule: To subtract in algebra, add the opposite so
7 - (+ 9) is the same as 7 + (-9).
8-2
8 - (-1)
9
Explanation: 8 - (-1) is the same as
8 + (+1)
-3 - (-4) = 1
True or False?
True
Explanation: -3 - (-4) is the same as -3+ (+4), which is 1.
13 - ( - 2)
Are we moving left or right of the number line?
Right
Rule: To subtract in algebra, add the opposite. So
13 - ( -2) is the same as 13 + ( +2)
-3-5
-8
Explanation: -3-5 is the same as -3 + (-5)
5 - (+4)
1
Explanation: 5 - (+4) is the same as
5 + (-4)
10 - (- 15) = -5
True or False?
False
10 - (-15) is the same as 10 + (+15) which is 25.
-18 - ( - 8)
Are we moving to the right or left of the number line?
Right
Rule: To subtract in algebra, add the opposite. So -18 - ( - 8) is the same as - 18 + (+8)
-7 - (+5)
-12
Explanation: -7 - (+5) is the same as - 7 + (-5)
-6-6
-12
Explanation: -6-6 is the same as
-6 + (-6)
-14 - ( - 9) = 5
True or False?
False.
Explanation: -14 - ( - 9) is the same as
-14 + ( + 9) which is - 5
- 9 - ( + 1)
Are we moving to the left or right of the number line?
Left
Rule: To subtract in algebra, add the opposite. So
- 9 - ( + 1) is the same as - 9 + (-1)
I have a number, say 5. I subtract a second number from it. The result of the subtraction is 9. What was the number I subtracted from 5?
-4
Explanation: The expression is 5 - (-4) which is the same as 5 + (+4)
-821 - ( - 498)
- 323
Explanation: -821 - (-498) is the same as
-821 + (+498)
The Bigsby Building has 28 stories and three basement levels. Suppose you took the elevator from basement level 3 all the way to the 28th floor. The number of floors you would travel is 31.
True or False?
True. Represent basement level 3 as - 3.
So it is 28 - (-3), which is 31.
A helicopter hovers 58m above the ocean's surface. A submarine is resting 34m underwater, directly below the helicopter. What is the difference between the positions of these two objects?
Are we moving to the left or right of the number line?
Right
Rule: To subtract in algebra, add the opposite. So
58 - ( - 34) is the same as 58 + ( + 34)
The record high temperature for Pennsylvania is 111 degrees Fahrenheit. The record low is -42 degrees Fahrenheit. What is the difference between the high and low?
153 degrees Fahrenheit
Explanation: The expression is 111 - ( -42). This is the same as
111 + (+ 42)
What is the difference between Montana's record low of -70 degrees Fahrenheit and New York's record low of - 52 degrees Fahrenheit?
18 degrees Fahrenheit
Explanation: The sentence is -52 - (-70) which is the same as - 52 + (+70).