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

May 14, 2018

-28%

#### Explanation:

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

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

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%.)

May 14, 2018

$- 28$ 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

$\frac{\text{change"/" total" = "percent}}{100}$

putting these values into the equation gives

$\frac{0.27}{0.96} = \frac{x}{100}$

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

$x = \frac{0.27 \times 100}{0.96}$

$x = 28.125 \approx 28$

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

May 14, 2018

$- 27$ is the correct option.

#### Explanation:

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

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

This means that the $0.96 g$ 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 $0.96 g - 0.69 g = 0.27 g$

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.