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Finding percent of a number, percent increase/decrease
Learn step-by-step with practice exercises built right in.
Method: Convert percent to decimal, then multiply.
Example: What is 25% of 60?
What is 30% of 80?
Convert percent to decimal and multiply:
Avoid these 3 frequent errors
See how this math is used in the real world
Solve .
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Can be rearranged:
Example: Price increases from \20$25$:
Example: Price drops from \40$30$:
Discount: amount saved Sale price = Original price - Discount
Tip/Tax: added amount Total = Original + Tip (or Tax)
Answer:
A shirt costs \40$. It is on sale for 25% off. What is the sale price?
Method 1: Find discount, then subtract
Method 2: Multiply by (1 - 0.25)
Answer: \30$
A population increased from 250 to 300. What is the percent increase?
Use percent increase formula:
Answer: 20% increase
A jacket originally costs $80. It goes on sale for 30% off. What is the sale price?
Method 1: Find discount, then subtract Step 1: Find 30% of 24 discount
Step 2: Subtract from original. 24 = $56
Method 2: Find what you pay directly Step 1: If 30% off, you pay 70%. 100% - 30% = 70%
Step 2: Find 70% of 56
Answer: $56
You got 17 out of 20 questions correct on a test. What is your percentage score? Then, if the teacher adds 5 bonus points to your raw score, what is your new percentage?
Part 1: Original percentage Step 1: Set up the fraction. 17/20
Step 2: Convert to decimal. 17 ÷ 20 = 0.85
Step 3: Convert to percent. 0.85 = 85%
Part 2: With bonus points Step 1: New score. 17 + 5 = 22 points earned Total still out of 20 (bonus goes above 100%)
Step 2: Calculate percent. 22/20 = 1.10 = 110%
Answer: Original: 85%, With bonus: 110%