How to Find a Percentage of a Number: Grade 6

To find a percentage of a number means to take that many parts out of every 100 parts of it. I use two methods: the 10% method, which starts with one tenth, and the fraction method, which turns the percentage into a fraction or a decimal and multiplies. Both land on the same answer, so your child can pick the one that feels easier.

What Does “Find 20% of 80” Mean?

Find 20% of 80 means take 20 parts out of every 100 parts of 80. Picture 80 split into 100 equal pieces, and keep 20 of those pieces. That picture stops the commonest error, which is finding the percentage of the wrong whole.

I start with a pile of 80 counters. Split them into 100 equal parts, and each part is 0.8 of a counter. Keep 20 parts, and you hold 16 counters. The picture is fiddly, so in class I use the methods below instead.

If the word percentage still feels new, read my What Is a Percentage? guide first.

Method 1: Start With 10%

Start with 10% because 10% of any number is easy: just move the point one place left, or divide by 10. So 10% of 80 is 8, and 20% is double that, which is 16. 10% of 200 is 20, so 20% is 40 and 5% is 10, which adds to 50.

Ten percent is the friendliest number in the topic. To find 10%, move the point one place left: 10% of 200 is 20, 10% of 80 is 8, and 10% of 250 is 25. One move, no calculator.

From 10%, build the rest. For 25% of 200, take 20% (40) and 5% (10), then add them to get 50. For 30% of 80, take 10% three times: 8 + 8 + 8 = 24. Small steps beat one big leap.

Method 2: Turn the Percentage Into a Fraction or a Decimal

Turn the percentage into a fraction or a decimal, then multiply. So 20% is 20/100, which is 1/5, and 1/5 of 80 is 16. For 25% of 200, write 25% as 0.25, and 0.25 times 200 is 50. This method works for any percentage, even the awkward ones.

Fractions suit neat percentages. 50% is 1/2, 25% is 1/4, 20% is 1/5 and 10% is 1/10. I ask children to learn these four by heart, because they turn most sums into one easy division.

Decimals suit the rest. For 37% of 200, write 0.37 and multiply: 0.37 × 200 = 74. The decimal method works for any percentage, even the awkward ones.

How Do You Find 1% of a Number?

To find 1% of a number, divide it by 100. So 1% of 200 is 2, and 1% of 80 is 0.8. One percent is the building block for any percentage, so once you have 1%, you can build 5%, 10% or 37%.

One percent is the smallest brick in the wall. Divide by 100, which moves the point two places left: 1% of 200 is 2, and 1% of 80 is 0.8. From 1%, build any percentage by multiplying.

For 37% of 200, find 1% first (2), then multiply by 37 to get 74. It is slower than the 10% method, but it never fails, and I teach it to children who like a method they can trust.

This is the skill Common Core standard 6.RP.A.3 asks for: find a percent of a quantity as a rate per 100.

What Mistakes Do Children Make Most When Finding a Percentage of a Number?

The biggest mistake is finding the percentage of the wrong whole, like taking 20% of the sale price instead of the full price. Children also forget to divide by 100, and they mix up 10% and 1%. Each mistake comes from rushing, so I make children name the whole first.

The wrong whole is the trap I see most. A child takes 20% of the sale price instead of the full price, and the answer comes out too small. I make children point at the whole and say it out loud before they start.

Forgetting to divide by 100 is the second trap. A child multiplies 20 by 80 and gets 1,600, which is nonsense for a percentage of 80. Divide first, then multiply, and the answer stays sensible.

A Real-Life Case: A Shirt on Sale

Here is one case, worked in full, the way I do it in class.

Step 1: A shirt costs Rs. 800, and the shop gives 25% off. The whole is Rs. 800, and the discount is 25% of it.

Step 2: Find 25% of 800. Ten percent is Rs. 80, so 20% is Rs. 160 and 5% is Rs. 40. Add them: Rs. 160 + Rs. 40 = Rs. 200 off.

Step 3: Take the discount off the full price: Rs. 800 minus Rs. 200 = Rs. 600. You pay Rs. 600 for the shirt.

I show more discount sums in my How Percentages Work in Shopping guide.

For more practice with money, speeds and percentages, try my Ratio, Rate and Percentage Application worksheet.

Try It Yourself: 3 Practice Questions

Cover the answers, try all three, then check.

1. Find 50% of 90.
2. Find 10% of 250.
3. Find 20% of 150.

Answers

1. 45. Half of 90 is 45, and 50% means a half.
2. 25. Move the point one place left: 10% of 250 is 25.
3. 30. Ten percent of 150 is 15, so 20% is double that, which is 30.

Key Takeaways

• 10% method: move the point one place left, then build up.
• Fraction method: turn the percentage into a fraction or a decimal, then multiply.
• 1%: divide by 100, then build any percentage from it.
• Name the whole: a percentage of the wrong whole gives a wrong answer.
• Divide first: turn the percentage into a part before you multiply.

If your child answered all three questions, she is ready for a longer page. For more free practice at this level, browse our Grade 6 math worksheets page. Every sheet is free to print.