The cost price of 27 articles is same as the selling price of 18 articles. What is the profit percent?

Let the cost price of 1 article be CP and the selling price of 1 article be SP.
According to the question:

27×CP=18×SP
Rearranging the terms to find the ratio of SP to CP:

CP
SP
​
=
18
27
​
=
2
3
​

This means if CP=2, then SP=3.

Profit=SP−CP=3−2=1
Profit Percent=(
CP
Profit
​
)×100%
Profit Percent=(
2
1
​
)×100%=50%