ASVAB Study Guide4.Percent Change
Finding a part, a whole, or a percentage in basic real-world scenarios.
Part = Whole × Percent or Percent = (Part / Whole) × 100
Percentages represent parts of a whole quantity based out of a scale of 100 units.
Example
What is 15% of 80?
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Step 1: Convert 15% to a decimal: $$\frac{15}{100} = 0.15$$
Step 2: Multiply the whole amount by the decimal: $$80 \times 0.15$$
Step 3: Calculate the final value: 12
Practice problems
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Problem 1
Out of 40 students in a class, 30% are enrolled in the music program. How many students are in the music program?
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Answer: 12 students
Step 1: Convert 30% to a decimal: $$\frac{30}{100} = 0.30$$
Step 2: Multiply the whole class size by the decimal: $$40 \times 0.30$$
Step 3: Calculate the final result: 12 students
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Problem 2
A mechanic completed 18 out of 24 planned vehicle inspections today. What percentage of inspections did they finish?
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Answer: 75%
Step 1: Set up the fraction of part over whole: $$\frac{18}{24}$$
Step 2: Convert the fraction to a decimal: $$\frac{18}{24} = 0.75$$
Step 3: Multiply by 100 to find the percentage: $$0.75 \times 100 = 75\%$$
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Problem 3
If 45 is 60% of a number, what is the value of that number?
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Answer: 75
Step 1: Convert 60% to a decimal: $$\frac{60}{100} = 0.60$$
Step 2: Set up the division equation: Whole = Part / Decimal
Step 3: Divide 45 by 0.60: $$\frac{45}{0.60} = 75$$
Always convert percentages to decimals by dividing by 100 before performing arithmetic calculations.