Return to Mathematics IndexAn Introduction to Percent

Kenneth Surdell Lewis School

1431 N. Leamington

Chicago, Ill. 60651

312-804-3060Objectives:

Fifth grade students will develop a basic understanding that percent is a

comparison of some number to 100.

Pupils will convert fractions to percent, percent to decimals and vice versa

with a minimum of 90% accuracy.Materials:

Per team: 2 sheets of 1cm^{2}graph paper; 2 pairs of scissors;

1 sheet of 100 squares. marked with 12% "A's". 16% "B's", 18% "C's",

5% "D's", 3% "E's", 8% "F's", 13% "G's" and 25% "H's".Strategy:

Develop the idea that percent is a comparison of some number to 100 which

can be written in the form of x with the sign % or x%. Think of the symbol % to

be a distortion of the 100 in a ratio of x:100. The ratio of 20 to 100 is 20

percent or 20% and this is the same as 20 hundredths or 0.20. Therefore, 20

parts per hundred can be renamed as 20/100, 20% or 0.20.

Show 50/100 as .50 as 50%. Follow up with 75/100, 30/100, 10/100, etc. Have

pupils rename other ratios of 100 as percent and decimal.

We know that 50/100 = 1/2, 75/100 = 3/4, 20/100 = 1/5 therefore we can show

that 1/2 is 50%, 3/4 is 75% and 1/5 is 20%.

To convert fractions whose denominator is something other than 100, you must

first rename the fraction with a denominator of 100.

Divide the students into teams of 3 or four. Have one student in each team

cut a 10cm by 10cm square off a graph sheet. Count the number of sq. cm. in the

square. There are 100 sq. cm. On chalkboard write this value as100/100 =100%. Point out that 100% isallof the squares or 100 squares.

Cut a second 10 by 10 square. Compare it with the first. They're equal.

Now cut this second sheet in half. Count the number of square cm. in each half.

There are 50. On the chalkboard show this as50/100 = 50%. Since 50/100 is

half of the 100 original squares we can say that 50/100 = 1/2 which also equals

50%.

Follow the above sequence and have the students cut out 25, 20, 10, 1

squares. Compare them to the original 100, write them as fractions of a

hundred and convert the fraction to percent.

Use the graph sheet marked with letters "A" to "H". Count the number of

"A's". Write as a fraction of 100 (12/100). Convert to percent (12%).

Continue the same procedure with the other letters.

Have teams make up a letter sheet of their own, exchange with other teams and

determine the percent of each of the letters.

Pupils should be able to convert percent to a fraction with a denominator of

100 and rename the fraction as a decimal.