Decimals & Percents · Percent of a number · 6.4

What percent is it?

To find what percent one number is of another, write part over whole as a fraction, turn it into a decimal, and multiply by 100. 12 out of 80 = 12/80 = 0.15 = 15%.

01 / THE IDEA

See it work.

Watch the method

What percent is A of B?

12 of 80 = 12/80 = 15%.

1 / 2
What % of 80 is 12?\text{What \% of } 80 \text{ is } 12?
1

Make a fraction

Part over whole.

1280\frac{12}{80}
2

Convert to a percent

×100 and add %.

=15%= 15\%
02 / YOUR TURN

Practice until it feels automatic.

Your turn

Work it out.

Type a percent, e.g. 25%.

streak 0
best 0
… =
— / WHY IT WORKS

The idea underneath.

Part over whole

Divide the part by the whole, then ×100 to express it as a percent.

Why it works

12 out of 80 is 15%.

03 / WORKED EXAMPLES

From easy to tricky.

EX 1easy

What percent of 40 is 20?

1

Make a fraction

Part over whole. 20/40

2

Convert to a percent

×100 and add %. = 50%

EX 2medium

What percent of 50 is 5?

1

Make a fraction

Part over whole. 5/50

2

Convert to a percent

×100 and add %. = 10%

EX 3hard

What percent of 80 is 60?

1

Make a fraction

Part over whole. 60/80

2

Convert to a percent

×100 and add %. = 75%

04 / COMMON TRAPS

Where students slip.

Trap

Putting the whole over the part.

Fix

It’s part ÷ whole, not whole ÷ part.

Trap

Forgetting the ×100.

Fix

Turn the decimal into a percent.

05 / QUIZ

Test yourself.

The Test

12 problems across three tiers. Auto-graded on submit. Hints and a full walkthrough on every question. Your work is saved on this device — sign in to keep it across devices.

0/12Answered
How to answerType just the value. Formatting won't trip you up — we ignore spaces, capital letters, commas, and subscript style, so t₁ = 5, d = 3 and t1=5,d=3 both count. For a list of numbers, separate them with commas (e.g. 3, 10, 17).
Core

Core (4)

C1

What percent of 20 is 2?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
C2

What percent of 25 is 6.25?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
C3

What percent of 25 is 2.5?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
C4

What percent of 40 is 8?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
Apply

Apply (4)

A1

What percent of 20 is 15?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
A2

What percent of 80 is 16?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
A3

What percent of 80 is 40?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
A4

What percent of 25 is 6.25?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
Extension

Extension (4)

E1

What percent of 80 is 8?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
E2

What percent of 50 is 5?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
E3

What percent of 100 is 50?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.
E4

What percent of 100 is 25?

Need a hint?
  • Write part ÷ whole.
  • Multiply by 100.