Decimal Number ConceptsBasic College Mathematics for Teachers

Reference: K. Elayn Martin-Gay – Page 1    Definition:  Decimal

# Change Words to Numerals

Eight Tenths  =  .8

Thirty-Four Hundredths  =  .34

Nineteen Thousandths  =  .019

# Change Numerals to Words

.3  =  Three Tenths

.59  =  Firty-nine Hundredths

.008  =  Eight Thousands

# Place Value of Decimal Numbers

Position of a Decimal Numeral has Value

Tenths      Hundredths

Thousandths      TenThousandths

HundredThousandths

# Rounding Off Decimal Numbers

If  N<5 Rd. Dn    If N=5 Rd. Up   If  N>5 Rd.Up

Round each Decimal to Hundredths

.342  Rd to Hths  = .34

.345  Rd to Hths  = .35

.347  Rd to Hths  = .36

Line Up Decimals   or

Find a Common Denominator

.3  +  .45  =  .75

.67  +  .02  =  .69

Decimals are special Fractions

with Denominators of 10, 100, etc…

# Subtraction of Decimal Numbers

Line Up Decimals  or

Find a Common Denominator

.67  -  .5  =  .17

.8  -  .03  =  .77

Decimals are special Fractions

with Denominators of 10, 100, etc…

# Multiplication of Decimal Numbers

Multiply Numbers then determine

numbers behind decimals   Rt = Lt

.3  x  .05  =  .015

.02  x .03  =  .0006

Decimal Places  Rt  =  Decimal Places Lt.

# Division of Decimal Numbers

Divide Decimals but first move

decimal point on  outside & inside

.15  /  .5  =  .3

____                    ___

.5  |  .15      =>      5  | 1.5

Decimal Moves Rt  =  Decimal Moves Rt

Thomas Love            Malone College          2006/2008

Decimal Number ConceptsBasic College Mathematics for Teachers

Reference: K. Elayn Martin-Gay – Page 2    Definition:  Decimal

Fractions to Decimals

Divide Denominator into Numerator

3 / 4 =  .75

4 ) 3.00

4 / 5 = .8

5 )  4.00

# Decimals to Fractions

Decimals are special Fractions with

Denominators of 10, 100, 1000, etc…

.3  =  3  / 10

.45 = 45 / 100

# Terminating Decimals

Decimals that stop or do not repeat!

.6

.75

.009

# Repeating Decimals

Decimals that repeat over & over!

.777777…

.1666666…

.833333…

# Compare:<  =>

(8/100)       .08 < .75       (75/100)

(3/10)     .3  =  .3     (3/10)

(60/100)      .6  >  .09      (9/100)

Change to Fractions & Check as Fractions!

# Compare:<  =>

(  )       .09  __  .75       (   )

(3/10)     .1  __  .1     (3/10)

(   )      .4  __  .07      (   )

Change to Fractions & Check as Fractions!

Order Decimals:  Hi to Lo

Given:     .3     .09     .75

Order from Hi to Lo

.75,   .3   .09

# Order from Lo to Hi

.09,   .3,   .75

Order Decimals:  Hi to Lo

Given:     .9     .07     .45

Order from Hi to Lo

____    ____    ____

# Order from Lo to Hi

____    ____    ____

Thomas Love            Malone College          2006/2008