Praxis Core Academic Skills for Educators: Mathematics (5733)Number and QuantityEasy
A botanist is tracking the growth of a plant. On Monday, the plant was 18.5 cm tall. By Friday, it had grown by 15%. What was the plant's height on Friday?
- A21.275 cm
- B33.5 cm
- C2.775 cm
- D15.725 cm
Show answer & explanationAnswer & explanation
Correct answer: A. 21.275 cm
To find the plant's height on Friday, first calculate 15% of 18.5 cm, then add that growth to the original height. This will give the new total height.
Why the other options are wrong
- B. This is the result of adding 18.5 and 15, treating 15 as a value rather than a percentage.
- C. This is only 15% of the original height, not the new total height.
- D. This represents the original height minus 15% of the original height, indicating a decrease.
Percentage Increase
A percentage increase is calculated by finding a percentage of an original value and then adding that amount to the original value. It shows a growth in quantity.
- New Value = Original Value + (Percentage Increase * Original Value)
- Can also be calculated as Original Value * (1 + Percentage Increase as Decimal)
- Essential for financial growth, population changes, etc.
Memory trick: To grow by percent, multiply and then add, or use the 1-plus-decimal method, it's not bad!