If an object went from #0.96g " to " 0.69g# would the percent change be #-28# or #-39# and why?
Always remember that a percentage change of two different values is the difference over the original.
The difference in the change is
Now, divide this value by the original value:
(Note, usually, the percentage change is taken to be the absolute value, i.e. ignore the sign to get
The ratio is
putting these values into the equation gives
Multiplying both sides by
The first clue is the negative sign, which indicates a decrease.
The mass changed from
This means that the
The amount of the decrease is
Determine what percent this is of the original amount.
As the change is a decrease this can be shown as
If the change was calculated using the final amount the answer is
However, this is incorrect.