Subtraction Rules
What should I change my subtraction problem to when solving?
Addition
Solve:
8-(-2)
8 + 2 = 10
- 3.5 - 4.8 =
-3.5 + (-4.8) =
-8.3
2/6 - 1/6 =
2/6 + (-1/6) =
1/6
-4 + 12 =
12 - 4 = 8
What is the first rule when subtracting fractions?
KEEP the first number the same
Solve: -3 - (- 4) =
- 3 + 4 = 1
-5.1 - (-5.1) =
- 5.1 + 5.1 =
0
(-1/5) - 3/5 =
(-1/5) + (-3/5) =
-4/5
-4.2 + 2.1 =
4.2 - 2.1 =
-2.1
What is the second rule I do when subtracting?
CHANGE to addition
Solve:
-5 - 5 =
-5 + -5 = -10
-5.2 - (-10.5) =
-5.2 + (10.5) =
5.3
1/4 - 5/8 =
1/4 + (-5/8) =
2/8 + (-5/8)=
5/8 - 2/8 =
- 3/8
- 5.2 - 10.5 =
-5.2 + (-10.5) =
5.3
What is the third and final thing I do when subtracting?
OPPOSITE of the second number
SOLVE:
2 - 9
2 + (-9) = -7
8.9 - (-2.5) =
8.9 + (2.5) =
11.4
1/2 - (-2/3) =
1/2 + (2/3) =
3/6 + 4/6 =
7/6 OR 1 and 1/6
-3/5 - 1/2 =
-3/5 + (-1/2) =
6/10 + 5/10 =
11/10 OR 1 and 1/10
Change this problem to addition.... -3 - (-4), then solve
-3 + 4 = 4 - 3 = 1
SOLVE:
-8 - (- 2) =
-8 + (2) = -7
18.6 - 11.23 =
18.6 + (-11.23) =
7.37
1 and 2/4 - 1 and 1/6 =
1 and 6/12 + (- 1 and 2/12)
1-1 = 0
6/12 - 2/12 =
4/12
1/3 - (-4/5) =
1/3 + (4/5) =
5/15 + 12/15=
17/15 OR 1 and 2/15