2.5 x 100 = 250
2.5 times 100 is 250. Multiplying by 100 moves the decimal point two places to the right, past the 5 and into an added zero. The percent version of this sum is a different number entirely.
2.5 × 100 = 250
Move the decimal point two places right
Multiplying by 100 slides the decimal point two places to the right. 2.5 has only one digit after the point, so the first move clears the 5 and gives 25, and the second move needs a zero to fill the empty column: 250.
The fraction check
2.5 is five halves. A hundred lots of five halves is 500 halves, and 500 divided by 2 is 250. Same answer by a different road, which is worth doing whenever you are unsure the point landed in the right column — the fraction route has no decimal point to misplace.
The percent trap
This is the calculation most often confused with its opposite. 2.5 x 100 = 250 says that 2.5, written as a percentage, is 250%. But 2.5% of 100 is 2.5, not 250: percent means “per hundred”, so that sum multiplies by 100 and divides by 100 and lands back where it started. If your context is a rate, a discount or an interest figure, decide which of the two you actually want before you reach for the answer.
The number 250
250 is a quarter of 1000 and half of 500, and factors as 2 x 5 x 5 x 5. Four of them make 1000, which is why 250 keeps turning up in quarter-of-a-batch quantities.
Nearby decimals
- 0.5 x 100 = 50
- 1.5 x 100 = 150
- 2.5 x 100 = 250
- 25 x 100 = 2500 — the same digits with the point moved, and ten times this answer.