Percentages Flashcards
What formula do you use for “What is X% of something?”
Finding a Part
“What is X% of…”
A teacher graded 150 assignments. 20% of the students got an A. How many students got an A?
Part = (Percentage / 100) * Whole
“What is X% of…”
(20/100) * 150 = 30
What formula do you use for “X% is this much. What is the total?”
Finding the Total
“What is the total?”
“After a discount, price is this much.”
If 30% of the students play basketball and that equals 90 students, what is the total number of students?
Total = = Part / (Percentage / 100)
“What is the total?”
“After a discount, price is this much.”
Whole = 90 / (30 / 100)
Whole = 90 / 0.30
Whole = 300
What formula do you use for “How much has it increased or decreased in %
Percentage Change
“Increased from… to…” “Decreased by…”
A city’s population grew from 5,000 to 6,500 people. What percentage did the population increase by?
Percentage Change = [(New Value - Original Value) / Original Value] * 100
Percentage Increase = [(6,500 - 5,000) / 5,000] * 100
Percentage Increase = [1,500 / 5,000] * 100
Percentage Increase = 0.3 * 100
Percentage Increase = 30%
How do you find the final price after a discount?
Finding the Final Price
A store is offering a 25% discount on jackets that cost $80. What is the final price after the discount?
Final Price = Original Price - (Discount Percentage x Original Price)
“What do I pay after discount?” “After X% discount…”
If the original price is $80 and the discount is 25%, the calculation would be: Final Price = $80 - (0.25 x $80) = $20
Then $80-$20=$60
After a discount, price is this much” “X% off, what was the price b4
Reverse Discount. Whats the OG price?
A table is on sale for $120 after a 40% discount. What was the original price of the table?
Original Price = Sale Price / (1 - Discount Percentage)
OG = $120 / (1 - 0.40)
OG = $120 / 0.60
Original Price = $200
What formula do you use for “What percentage is this of that?”
Finding Percentage
A student got 45 questions right on a 60-question test. What percentage did the student score?
Percentage = (Part / Total) × 100
“What percentage is this of that?” “What percent passed/scored?”
(Number of Correct Answers / Total Number of Questions) * 100
(45 / 60) * 100
0.75 * 100
75
How do you calculate the discount amount?
Finding the Discount Amount
A store offers 10% off on all $50 items. How much is the discount?
X% discount”
“How much is reduced?”
Discount = (X% / 100) × Original
X% discount”
“How much is reduced?”
