JentooSAT®

SAT® · Math: Problem-Solving and Data Analysis

Percentages At or Above 100 Percent

A percent above 100 just means more than one whole copy of the amount. 250 percent of a number is 2.5 times that number, not an error or an impossible value.

A percent is just a ratio to 100, so there is nothing stopping it from passing 100 once you're comparing two different amounts instead of splitting one whole into parts. If a number is 250 percent of another, that means for every 100 units the second number has, the first has 250 — in other words, the first is two and a half times the size of the second. Nothing is being carved up into pieces that must stay under one whole; you're just scaling.

The key move is converting the percent into a multiplier. 'x percent of a number' always means multiply by x/100 — no addition involved. But 'a p percent increase' means the new amount is the original plus p percent more of it, so the multiplier becomes 1 + p/100. A channel with 4800 subscribers that grows by 175 percent ends up with 4800 times (1 + 175/100) = 4800 times 2.75 = 13,200 subscribers, not 4800 times 1.75.

This distinction — 'percent of' versus 'percent increase' — is the same skill tested across ratio and growth problems in this unit: scatterplot trend lines, margin of error language, and repeated percent change all hinge on correctly identifying the multiplier before you compute. Mixing up the two phrasings is the single most common way these problems go wrong.

Key terms

Multiplier
The single number you multiply an original amount by to get the result of a percent change.
Percent increase
A change described as p percent more than the original, found by multiplying by 1 + p/100.
Percent of
A direct scaling of a quantity by x/100, with no original amount added back on.
Growth factor
Another name for the multiplier used to represent repeated or percent-based growth.

Watch it explained

  1. How it worksHow does 250 percent of a number mean two and a half copies of it?
  2. Worked exampleFind the new subscriber count when a channel with 4800 subscribers grows by 175 percent.
  3. Going furtherWhat does it mean for a price to be 140 percent of last year's price rather than 140 percent higher?
  4. Common mistakeWhy isn't a 200 percent increase the same thing as doubling?

Check yourself

Your turneasy1 of 3
A channel with 7179 subscribers grows by 211 percent over one year. How many subscribers does the channel have at the end of that year?

End of topic.