TEAS Math: How to Calculate Percent Change
Percentages appear in many real-world situations, from discounts and price increases to changes in measurements. They are also an important type of problem to practice when preparing for TEAS Math. The key is knowing which number should be used as the original amount.
The Percent Change Formula
A common formula is: Percent change = (change ÷ original amount) × 100 First find the difference between the new and original values.
Example: Percent Increase
Suppose a price increases from $40 to $50. The change is: 50 − 40 = 10 Now divide by the original value: 10 ÷ 40 = 0.25 Multiply by 100: 0.25 × 100 = 25% The price increased by 25%.
Example: Percent Decrease
Suppose a quantity decreases from 80 to 60. The change is: 80 − 60 = 20 Then: 20 ÷ 80 = 0.25 Therefore: 25% decrease
Why the Original Number Matters
One of the most common mistakes is dividing by the new value instead of the original value. Always ask: “What was the starting amount?” That is normally the denominator when calculating percent change.
Discounts and Price Problems
Percentage problems may also appear as discounts. For example, a $100 item is discounted by 20%. The discount is: $100 × 0.20 = $20 The final price is: $100 − $20 = $80
Practice Without a Calculator First
When possible, estimate your answer before calculating it. If something increases from 50 to 55, you should expect a relatively small percentage increase—not 50% or 100%. Estimation can help you catch calculation errors.
Final Takeaway
For TEAS percentage problems, identify the original value, calculate the difference, divide by the original amount, and convert the result to a percentage. Practicing different examples involving increases, decreases, and discounts can make these problems much easier.
