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20 decreased by 80% = 4

20 decreased by 80 percent is 4. Step-by-step solution with the formula and worked example.

20 decreased by 80% = 4
decreased by %

Solution: 20 decreased by 80 percent

Decrease = 80% × 20 = 16
Result = 20 − 16 = 4

Step-by-step explanation

  1. Find the decrease: 80% of 20 = 16.
  2. Subtract it from the original: 20 − 16 = 4.
  3. Shortcut: multiply by (1 − 80/100) = ×0.2.

Good to know

Shortcut: decreasing by 80% is the same as multiplying by 0.2 (that is 100% − 80%). So 20 × 0.2 = 4 in one step.

Frequently asked questions

20 decreased by 80 percent
20 decreased by 80% = 4.

How is it calculated?
See the step-by-step solution above — it uses the standard percentage formula.

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