20% of 30 is 6. Twenty percent is one fifth, and thirty divides cleanly by five: 30 ÷ 5 = 6. Decimals match: 0.2 × 30 = 6. On the same thirty, 15% of 30 is 4.5, 25% of 30 is 7.5, and 30% of 30 is 9—so the twenty-percent slice is the integer halfway between a fifteen-percent cut that needs pence and a quarter-plus band that overshoots six by one and a half.
Read 20% off £30 as “take off £6,” leaving £24 before shipping, VAT, or service. If the brief asks only for twenty percent of thirty—commission, cohort share, or a budget slice—the figure to quote is 6, not twenty-four. The discounted total only appears when the wording explicitly moves from “of” to “off” or “after discount.”
Neighbouring bases bracket this answer: 20% of 25 is 5, and 20% of 40 is 8, so thirty’s fifth sits at 6 on that line. Scale up by ten and 20% of 300 is 60—the same rate, same digit pattern, one decimal place shifted. That jump is a useful rehearsal for invoice lines that grow from a thirty-pound line item to a three-hundred-pound subtotal.
Thirty also factorises as 3 × 10, so you can think 20% of 10 = 2 (see 20% of 10) and triple the base to get 2 × 3 = 6. That decomposition is handy when your mental anchor is a tenner and the bill lists three of them rolled into one line.
If £30 is reduced by 20%, the reduction is £6 and you pay £24 (before other charges).
Change either value below to solve another percentage-of-number question instantly.
Formula used: (percentage ÷ 100) × number
Step 1: Convert 20% → 0.2.
Step 2: Multiply: 0.2 × 30 = 6.
Full formula: (20 ÷ 100) × 30 = 6
Fifth shortcut: 30 ÷ 5 = 6. Because both 20 and 30 share factors of ten in classroom examples, always divide the base (thirty) by five, not “thirty by twenty.”
Taking a fifth of thirty removes the factor of five from thirty’s 2 × 3 × 5 skeleton and leaves 2 × 3 = 6. That is the same product you get from doubling 10% of 30 (3), which shows two independent mental routes converging on one till-friendly integer.
Compared with 20% of 20 (4), adding ten to the base adds two pounds to the fifth—linear scaling again. If someone moves a quote from twenty to thirty pounds at the same twenty-percent rate, the fee or discount chunk grows by exactly two.
Fastest: 30 ÷ 5 = 6.
From 25% of 30 = 7.5, subtract 5% of 30 = 1.5 to return to 6—useful if your head anchors on quarters first.
Example 1: Twenty percent off a £30 shirt
The markdown is £6 and you pay £24 if nothing else is stacked on the ticket.
Example 2: Class trip kitty
If thirty pupils each put in a pound and the organiser sets aside 20% of the £30 float for first aid snacks, that reserve is £6, leaving £24 for transport lines if the rule is strict.
Example 3: Streaming add-on
A bolt-on quoted as 20% of a £30 bundle component costs £6; the remainder of that component’s headline would be £24 only if the wording describes a discount, not a surcharge on top.
Example 4: Order-of-magnitude check
Ten times the base moves you to 20% of 300 (60). If your spreadsheet shows 600 or 0.6 instead, you have likely misplaced the decimal tied to the percent conversion.
20% of 30 is 6.
Multiply 30 by 0.2, or divide 30 by 5 because 20% is one fifth.
20% off 30 is a reduction of 6, leaving 24.