What is 20% of 400?
The answer is 80.
Why Eighty on Four Hundred
Four hundred is 40 × 10, so 10% = 40 and doubling lands on 80 without leaving the tens pattern.
Against 20% of 100 (20): the base is four times larger, so the fifth is 20 × 4 = 80—a quick structural check whenever you see round hundreds.
Mental Maths Shortcuts for 20% of 400
Fastest: 400 ÷ 5 = 80.
- 10% of 400 = 40; double → 20% = 80.
- 20% of 300 = 60; add 20% of 100 = 20 → 80.
From 25% of 400 = 100, subtract 5% of 400 = 20 to land on eighty—useful if quarters come first mentally.
Real-World Examples
Example 1: Twenty percent off a £400 fee
The markdown is £80 and you pay £320 if nothing else stacks.
Example 2: Four-hundred-unit batch
If a 20% quality hold applies, 80 units are ring-fenced and 320 are free to ship under a strict rule.
Example 3: Budget line
Allocating 20% of a £400 sub-budget means £80 for that line and £320 notionally elsewhere—not the other way round unless the wording says “after discount.”
Example 4: Tenfold check
20% of 4000 is 800. If you see 80 or 8000 on the scaled row, revisit the percent-to-decimal step.
Common Mistakes
- Answering £320 when asked only for twenty percent of £400—three hundred and twenty is after the discount.
- Multiplying 20 × 400 without dividing by a hundred → 8000.
- Confusing 20% of 400 with “400 is 20% of what?” (400 ÷ 0.2 = 2000).
- Using 400 ÷ 20 as a percentage trick—it is not the fifth.
- Treating 0.2% of four hundred as twenty percent.
Related Links
FAQ
What is 20% of 400?
20% of 400 is 80.
How do you calculate 20% of 400?
Multiply 400 by 0.2, divide 400 by 5, or double 10% of 400 (40 → 80).
What is 20% off 400?
20% off 400 is a reduction of 80, leaving 320.