Percent Reference Sheet for solving part, whole, and percent problems using proportion, equation, and decimal methods.

Let’s solve each problem step by step using the proportion method shown in the reference sheet.

We’ll use this formula:
PART / WHOLE = PERCENT / 100

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Problem 1: Find the PART

*What is 20% of 40?*

Step 1: Set up the proportion.
PART / 40 = 20 / 100

Step 2: Cross-multiply.
PART × 100 = 40 × 20
PART × 100 = 800

Step 3: Divide both sides by 100.
PART = 800 ÷ 100 = 8

✔ Answer: 8

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Problem 2: Find the WHOLE

*15 is 25% of what number?*

Step 1: Set up the proportion.
15 / WHOLE = 25 / 100

Step 2: Cross-multiply.
15 × 100 = WHOLE × 25
1500 = WHOLE × 25

Step 3: Divide both sides by 25.
WHOLE = 1500 ÷ 25 = 60

✔ Answer: 60

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Problem 3: Find the PERCENT

*10 is what percent of 50?*

Step 1: Set up the proportion.
10 / 50 = PERCENT / 100

Step 2: Cross-multiply.
10 × 100 = 50 × PERCENT
1000 = 50 × PERCENT

Step 3: Divide both sides by 50.
PERCENT = 1000 ÷ 50 = 20

✔ Answer: 20%

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Now let’s do the second set (the ones with boxes and arrows):

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Problem 4: Find the PART

*What is 10% of 200?*

Step 1: Proportion → PART / 200 = 10 / 100

Step 2: Cross-multiply → PART × 100 = 200 × 10 → PART × 100 = 2000

Step 3: Divide → PART = 2000 ÷ 100 = 20

✔ Answer: 20

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Problem 5: Find the WHOLE

*30 is 60% of what number?*

Step 1: Proportion → 30 / WHOLE = 60 / 100

Step 2: Cross-multiply → 30 × 100 = WHOLE × 60 → 3000 = WHOLE × 60

Step 3: Divide → WHOLE = 3000 ÷ 60 = 50

✔ Answer: 50

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Problem 6: Find the PERCENT

*What percent of 100 is 25?*

Step 1: Proportion → 25 / 100 = PERCENT / 100

Wait — notice something? The whole is 100, so the part IS the percent!

But let’s do it properly:

Cross-multiply → 25 × 100 = 100 × PERCENT → 2500 = 100 × PERCENT

Divide → PERCENT = 2500 ÷ 100 = 25

✔ Answer: 25%

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Final Answer:
Problem 1: 8
Problem 2: 60
Problem 3: 20%
Problem 4: 20
Problem 5: 50
Problem 6: 25%