Rules for Decimals and Fractions
Decimals: All Operations ( + , -, x, ÷)
Adding and Subtracting Decimals:
When adding or subtracting decimals, make sure you LINE UP THE
DECIMALS AND BRING THE DECIMAL DOWN INTO YOUR ANSWER!
o Example: 52.369 + 12
52.369
12.000_
64.369
+
 (same rule applies for subtraction- line up decimals, bring
decimal in answer, subtract as normal)
o Example: 985 – 11.26
-
985.00
11.26
973.74
1)
Multiplying Decimals
Ignore the decimal points and multiply as usual...
2)
Count how many total digits are on the right side of
the decimal points in the guys you are multiplying...
3)
Place the decimal point in your answer so there are
this many digits to the right.
Multiply... Count the spots behind the decimals...
decimal point in your answer:
Put the
Dividing Decimals
dividend ÷ divisor = quotient
𝒅𝒊𝒗𝒊𝒅𝒆𝒏𝒅
𝒅𝒊𝒗𝒊𝒔𝒐𝒓
= 𝒒𝒖𝒐𝒕𝒊𝒆𝒏𝒕
1) Set up division problem in division house. Divi dend goes
inside the house and divisor outside the house.
2) Move the decimal point in the divisor to make the number a
whole number.
3) Move the decimal point in the dividend the same number of
places.
4) Immediately place the decimal point on top of the division
house and start dividing.
5) Follow the basic division steps: Divide, Multiply, Subtract,
Check, Bring Down - Repeat process until the problem stops
dividing (terminating decimal) or there is a pattern
(repeating decimal).
Add and Subtract Fractions and Mixed Numbers
When you add or subtract fractions you must have a common
denominator (LCD).
If you change the denominator you must also change the numerator.
Make sure all fractions are simplified and proper.
5 2

12 3
=
5
8

12 12
=
13
12
=
1
1
12
When Borrowing you must borrow a whole and keep the
denominators the same. (Hint: add the numerator and denominator)
2
5
4
- 3
5
5
_________
 You can’t take
2
4
away from so you need to borrow from the
5
5
5.
5
5
(always keep the denominators the same!) Don’t forget to
change the 5 to a 4!
5
2
2 5
7
 Add to
 4
+
= 4
5
5
5 5
5
7
 Subtract 4
5
4
-3
5
__________
3
1
5
 Borrow one whole from the 5 and rewrite the whole as
22
- 15
2
3
_________
 You can’t take
2
away from nothing so you need to borrow
3
from the 22.
3
3
(always keep the denominators the same!) Don’t forget to
change the 22 to a 21!
3
 Subtract 21
3
2
- 15
3
__________
1
6
3
 Borrow one whole from the 22 and rewrite the whole as
Multiply and Divide Fractions and Mixed Numbers
When you multiply and divide fractions, you must change all mixed
numbers and whole numbers into improper fractions. You may
cross simplify before you multiply.
8 5

25 16
=
1 1
 =
5 2
1
10
When you divide, you must “Leave, Change, Reciprocal.”
9 3

10 8
=
9 8

10 3
=
3 4

5 1
=
12
5
=
2
2
5