# One percent

One percent of all the lights in the city are LED, the remaining 99% are conventional. Other types are not there. John counted them honestly but he had counted only conventional. After a good dinner he registered numbers and he have notice that from all the lights that in this city he don't count LED contains 2%.

What percentage of lights in a city John counted?

Result

p =  50 %

#### Solution:

$0.01n / (n - p/100 \ n)=0.02 \ \\ 0.01 / (1 - p/100)=0.02 \ \\ 1=2 \cdot \ (1-p/100) \ \\ 0.5=p/100 \ \\ p=0.5 \cdot \ 100=50=50 \%$

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