Find a Percentage of a Find a Percentage of a NumberNumber

SWBAT use the percent formula to find SWBAT use the percent formula to find a percentage of a number; use a a percentage of a number; use a

percent proportion to find a percentage percent proportion to find a percentage of a numberof a number

ThinkThink

If Josie finds the perfect pair of shoes that If Josie finds the perfect pair of shoes that are originally $29.99, but are on sale at are originally $29.99, but are on sale at 10% off, how much money will she save?10% off, how much money will she save?

Percent FormulaPercent Formula

Percentage FormulaPercentage Formula Rate (r) Rate (r) · Base (b) = Percentage (p)· Base (b) = Percentage (p) rb=prb=p Write the percent as a decimal (rate)Write the percent as a decimal (rate) Multiply it by the whole number (base)Multiply it by the whole number (base) This gives the percentage of the numberThis gives the percentage of the number

Percent ProportionPercent Proportion

percentagepercentage percentpercent

base 100base 100 Use cross products and solve for the Use cross products and solve for the

percentagepercentage

=

ExamplesExamples

40% of 4540% of 453% of 803% of 80111% of 32111% of 320.6% of 300.6% of 3060% of 4060% of 40115% of 90115% of 908% of 2608% of 2600.4% of 500.4% of 50

Try TheseTry These

28% of 280028% of 2800 .28 .28 ·· 2800 2800 784784

0.2% of 47500.2% of 4750 .002 .002 ·· 4750 4750 9.59.5

300% of 92300% of 92 3 3 · 92· 92 276276

28% of 280028% of 2800 x/2800 = 28/100x/2800 = 28/100 100x = 78400100x = 78400 784784

0.2% of 47500.2% of 4750 x/4750 = .2/100x/4750 = .2/100 100x = 950100x = 950 9.59.5

300% of 92300% of 92 x/92 = 300/100x/92 = 300/100 100x = 27600100x = 27600 276276