Percentage and Rule Of Three

"Percentage" is the result obtained by multiplying a quantity by a percent, so 10 percent of 50 apples is 5 apples: the 5 apples is the percentage. + Y (5 apples) + P (10%) + X (50 apples)

Basic Formula

X/Y = P*100

Basic Problems

• Find P percent of X
• Find what percent of X is Y
• Find X if P percent of it is Y

Variations

• Y (Percent)
• P (Percentage)
• X (Total)

Y = (P/100) * X

• P percent of X is what? (5% of 29 is 1.45)
• What is P percent of X? (10% of 25 is 2.5)
• What of X is P percent? (2.75 of 25 is 11%)

P = (Y/X) * 100

• Y is what percent of X? (12 is 30% of 40)
• Y of X is what percent? (9 of 13 is 69.23%)
• What percent of X is Y? (22.22% of 27 is 6)

X = Y/(P/100)

• Y is P percent of what? (9 is 60% of 15)
• Y of what is P percent? (4 of 33.3333 is 12%)
• P percent of what is Y? (20% of 35 is 7)

Rule Of Three

It allows you to solve problems based on proportions.

Basic Formula

A/B = C/X

Sources

• Percentage: Edward Furey (Calculator Soup)
• Rule Of Three: Manual do Mundo

Tests