Press Start for 10%, 5% and 1% of a number, then type each answer on the number pad.
per min1% of 8100Press Start, then type or tap the answer. No Enter needed. The clock starts when you press Start.
More options
10%, 5% and 1% of a number, mixed: the three that the small percentages and the tens-and-fives drills build on.
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1 min of questions. An answer is checked as soon as it has enough digits. The result is correct answers per minute; a wrong answer counts against accuracy.
These mental math percentages drills ask one thing, a percent of a number, and every answer is whole. They run from 1% of a round number up to 200%, each with one way to do it in your head.
Read the full guide
Start from 10% and 1%
10% drops the last zero and 1% drops two. 5%: half of 10% and 20%: double 10% follow from there, and 35%, 45%, 65% and 85% are built from tens and fives. The Drill menu is under More options.
Flip it
A percent of a number is the same both ways around: 16% of 50 is 50% of 16, which is 8. Three drills use the swap, on 50, 25 and 20.
Over 100%
150% is the number plus half of it, and 125% is the number plus a quarter: 125% of 84 is 84 + 21 = 105.
Questions and answers
How do you work out percentages in your head?
Find an easy percent first and build from it. 10% drops a zero, 5% is half of that and 1% drops two zeros. So 35% of 80 is three tens, 24, plus one five, 4, which is 28.
Why is 16% of 50 the same as 50% of 16?
Both are 16 × 50 ÷ 100, and a multiplication gives the same answer in either order, here 8. The swap is worth making when one of the two is an easy percent, such as 50, 25 or 20.
Does this page do discounts or percent change?
No. It drills one form only: a percent of a number, with a whole answer. A price after a discount, or what percent one number is of another, is never asked.
Where are the drills on quarters and on 15%?
On mental math practice, under Percentages: the drills Quarter, half and three quarters and Fifteen percent. They are not repeated here.
All 15 drills
Small percentages 3
1% of a round numberDrop two zeros: 1% of 4,700 is 47.
2%, 3% and 4%Find 1%, then multiply: 3% of 700 is 7 × 3 = 21.
6% to 9% of round hundreds1% of a round hundred is its first digit, so 8% of 600 is 8 × 6 = 48.
Tens and fives 4
5%: half of 10%Find 10% and halve it: 5% of 360 is half of 36, 18.
10% of a numberDrop the last zero: 10% of 470 is 47.
20%: double 10%Find 10% and double it: 20% of 85 is 8.5 doubled, 17.
35%, 45%, 65% and 85%Build it from tens and fives: 35% of 80 is three tens, 24, plus one five, 4, so 28.
Flip it 3
Even percentages of 50Swap the two numbers: 16% of 50 is 50% of 16, which is 8.
Percentages of 20Swap and take a fifth: 35% of 20 is 20% of 35, a fifth of 35, 7.
Percentages of 25Swap and take a quarter: 36% of 25 is 25% of 36, a quarter of 36, 9.
Over 100% 3
110% and 120%The number plus 10% of it, once or twice: 120% of 250 is 250 + 25 + 25 = 300.
125% of a numberThe number plus a quarter of it: 125% of 84 is 84 + 21 = 105.
150% and 200%150% is the number plus half of it, and 200% is double: 150% of 46 is 46 + 23 = 69.
Mixed 2
10%, 5% and 1% warm-up10%, 5% and 1% of a number, mixed: the three that the small percentages and the tens-and-fives drills build on.
All four groups mixedTwo drills from each group in one run: small percentages, tens and fives, flips and over 100%.