Question

If an object went from `0.96g " to " 0.69g` would the percent change be `-28` or `-39` and why?

Answer 1

`-28%`

Explanation:

Always remember that a percentage change of two different values is the difference over the original.

The difference in the change is `0.69g-0.96g=-0.27g`.

Now, divide this value by the original value: `(-0.27g)/(0.96g)=-28.125%~~-28%` to get the percentage change.

(Note, usually, the percentage change is taken to be the absolute value, i.e. ignore the sign to get `28%`.)

Answer 2

`-28` because `0.96` is the starting value and therefore the base of the ratio for percentage change.

Explanation:

`0.96 - 0.69 = 0.27`

`0.27` = the change
`x` = the change in percent
`0.96` = the total starting value.
`100` = the total percent.

The ratio is

`"change"/" total" = "percent" /100`

putting these values into the equation gives

`0.27/0.96 = x/100`

Multiplying both sides by `100` and dividing by `0.96` gives

`x = (0.27 xx100)/0.96`

`x = 28.125 ~~28`

Because the `0.96` is the starting value it is the base of the ratio.

Answer 3

`-27` is the correct option.

Explanation:

The first clue is the negative sign, which indicates a decrease.

The mass changed from `0.96g` to `0.69g`

This means that the `0.96g` is the starting value. Any change, whether an increase or decrease, is calculated as a percentage of the original amount.

The amount of the decrease is `0.96g-0.69g= 0.27g`

Determine what percent this is of the original amount.

`0.27/0.96 xx 100%`

`= 28.125 ~~ 28%`

As the change is a decrease this can be shown as `-28%`

If the change was calculated using the final amount the answer is `39%`

`0.27/0.69 xx 100% = 39%`

However, this is incorrect.