School lesson Converting fractions, decimals and percents.

This was the lesson Mr.Isfeld taught last Wednesday Nov.9, 2011.

It was about converting fractions, decimals and percents.

Fractions to decimals

Example 1: Express 3/4 as a Decimal

Step 1: We can multiply 4 by 25 to become 100

Step 2: Multiply top and bottom by 25:

×25
3	=	75
4		100
×25

Step 3: Write down 75 with the decimal point 2 spaces from the right (because 100 has 2 zeros);

Answer = 0.75

Example 2: Express 3/16 as a Decimal

Step 1: We have to multiply 16 by 625 to become 10,000

Step 2: Multiply top and bottom by 625:

×625
3	=	1,875
16		10,000
×625

Step 3: Write down 1875 with the decimal point 4 spaces from the right (because 10,000 has 4 zeros);

Answer = 0.1875

Example 3: Express 1/3 as a Decimal

Step 1: There is no way to multiply 3 to become 10 or 100 or any "1 followed by 0s", but we can calculate an approximate decimal by choosing to multiply by, say, 333

Step 2: Multiply top and bottom by 333:

×333
1	=	333
3		999
×333

Step 3: Now, 999 is nearly 1,000, so let us write down 333 with the decimal point 3 spaces from the right (because 1,000 has 3 zeros):

Answer = 0.333 (accurate to only 3 decimal places !!)

Example: Express 0.75 as a fraction

Step 1: Write down 0.75 divided by 1:

0.75

1

Step 2: Multiply both top and bottom by 100 (there were 2 digits after the decimal point so that is 10×10=100):

× 100
0.75	=	75
1		100
× 100

(Do you see how it turns the top number
into a whole number?)

Step 3: Simplify the fraction (this took me two steps):

	÷5		÷ 5
75	=	15	=	3
100		20		4
	÷5		÷ 5

Answer = ³/₄

Note: 75/100 is called a decimal fraction and 3/4 is called a common fraction !

Decimals to Fractions

Example: Express 0.625 as a fraction

Step 1: write down:

0.625

1

Step 2: multiply both top and bottom by 1,000 (there were 3 digits after the decimal point so that is 10×10×10=1,000)

625

1,000

Step 3: Simplify the fraction (it took me two steps here):

	÷ 25		÷ 5
625	=	25	=	5
1,000		40		8
	÷ 25		÷ 5

Answer = ⁵/₈

Percent to Decimals

this link will help decimals.html">http://www.mathsisfun.com/converting-fractions-decimals.html