Question

2500 + 20%=what's the answer

Answer 1

Answer:

  as written: 2500.2

  as intended: 3000

Step-by-step explanation:

20% = 0.2, so adding 0.2 to 2500 gives 2500.2

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We suspect you want to add 20% of 2500 to 2500. That is ...

  2500 + 20%×2500

  = 2500 + 0.20×2500

  = 2500 + 500

  = 3000

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Comment on percentages

A percentage is a pure number. It is a ratio of like quantities, so has no units.* A useful percentage always has a base. That is, it is a percentage of something. Sometimes that base may be unclear or unstated, in which case the percentage might very well be considered to be meaningless.

In any event, a percentage is simply a (unitless) fraction. The "%" symbol means the same thing as "/100", so 20% means 20/100 = 2/10 = 1/5.

The very clear math expression 2500 +20% means simply 2500 + 1/5, which is the mixed number 2500 1/5 or the decimal value 2500.2. Usually, when we want to add a percentage to some value, we want the percentage to be of the original value. When that is written as a math expression, it must show this:

  2500 + 20% of 2500

  2500 + 20%×2500

  2500(1 +20%)

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* The concentration or potency of some medicines or other mixtures may be expressed as a percentage that is the ratio of one unit to a different unit, typically weight per volume. That is, a "0.1%" preparation may be 0.1 grams per 100 mL, for example. You have to read the label to determine whether this is the case. Mathematically, this is not a percentage, but is a non-standard use of the "%" symbol to indicate a ratio to 100 of something.