Answer:
If you have 10 phones, this is the 100%
then:
10 = 100%
Now we know that only 3 of them work correctly, then the percentage of pones that works correctly can be related to:
3 = X%
To find the value of X%, we can take the quotient of the equations:
3 = X%
and
10 = 100%
We ge:
(3/10) = (X%/100%)
We solve this for X and we get:
(3/10)*100% = X% = 30%
As we already know.
Now let's see how this percentage changes if we add more phones that do not work correctly.
Now we add another phone that does not work, so we have a total of 11 phones and 3 of them work.
then:
3 = X%
11 = 100%
The quotient is:
(3/11) = (X%/100%)
(3/11)*100% = X% = 27.3%
If we add another phone, now we have 12 phones and only 3 of them works, then 12 is the 100%, and we have the equations:
3 = X%
12 = 100%
Then we get:
(3/12) = X%/100&
(3/12)*100% = X% = 25%