The sprint is a survival run. The clock starts at one minute. Each correct answer adds 3 seconds to the clock. The run ends when the clock reaches zero, or when you solve the 50th problem.
The quiz shows one percent problem at a time. The problems get harder every 5 answers, in 10 levels. Level 1 is "50% of 80". Level 10 is "12.5% of 640" and two changes in a row.
How to play
The clock starts at your first keystroke, not when the page opens.
You start with one minute. Each correct answer adds 3 seconds.
Problems come one at a time, in order. You cannot skip a problem.
Type the answer as a whole number. An exact match commits at once. Enter is optional.
For a "? %" problem, type the percent only, without the % sign.
A wrong answer on Enter shakes the box and clears it. There is no penalty, but the clock keeps running.
Every 5 answers, the problems move up one level. There are 10 levels.
The run ends when the clock reaches zero, or when you solve all 50 problems.
Your score is the number of problems you solved. A full 50 ranks by time: the fastest player is first.
Select "Review answers" on the result screen to see each problem you played, with its answer.
What counts in this quiz
Up to 50 problems per run, in 10 levels of 5. Every answer is a whole number.
Level 1: 50% and 10% of round numbers. Level 2: 25%, 20%, 75% and 5%. Level 3: 1% to 9% of hundreds. Level 4: the other multiples of 5. Level 5: "12 of 48 = ? %".
Level 6: increase or decrease a number by a percent, such as "200 − 15%". Level 7: awkward percents of round numbers, such as "17% of 300". Level 8: find the whole, such as "30% of ? = 24". Level 9: percent change, such as "From 80 to 100: +? %". Level 10: fractional percents, percents above 100, and two changes in a row.
What's not included, and why
No decimals in an answer. Every base is chosen so the percent divides out to a whole number.
No rounding. If a problem looks like it needs rounding, look again: the exact answer is a whole number.
No problem asks for 100% of a number. The same problem never appears twice in one run.
Good to know
"Percent" comes from the Latin per centum, "by the hundred". The % sign grew out of a scribbled abbreviation of that phrase in 15th-century Italian ledgers.
x% of y is always the same as y% of x, because both are x × y ÷ 100. So 8% of 25 is 25% of 8, which is 2.