If 20 is 10% of a number, what is the original number?
200. Because 20 = 0.10 × whole → whole = 20 ÷ 0.10 = 200.
Detailed answer
Translate “10% of x is 20” into 0.10 × x = 20. Divide both sides by 0.10: x = 20 / 0.10 = 200. You can also think: if 20 is one-tenth, the whole is ten times 20. The calculator’s Basic tab outputs “10% of 200 = 20” as a cross-check.
Relationship context
Same algebra for any part-and-percent-known problem: whole = part ÷ (percent ÷ 100), as long as the percent is of that same whole.
Worked example
Algebra: whole = 20 ÷ (10 ÷ 100).
Same math as the live tool: Basic Percentage, Percentage Change, Percentage Of, and Value After Change.
Percentage Calculator modes
One page covers four patterns: percent of a total, part-to-whole percent, percent change between two values, and final value after a percent increase or decrease—with recent history on your device.