The answer is 17%.
First, we need to calculate what is the marked price. If it is 30% on the cost price, then the marked price is 130% (100% + 30% = 130%) of the cost price.
$155 is 100%, and we need to find out how much is 130% of $155:
$155 : 100% = x : 130%
x = $155 · 130% ÷ 100%
x = $201.5
Thus, the hardware store owner marked the refrigerator to sell for $201.5.
But, at the end, he sold it for 10% less than the marked price. In other words, he sold it for 90% (100% - 10% = 90%) of the marked price, and we need to calculate this percent.
Now, $201.5 is 100%, and we need to find out how much is 90% of $201.5:
$201.5 : 100% = x : 90%
x = $201.5 · 90% ÷ 100%
x = $181.35
Next, we want to calculate percent profit.
Here, $155 is cost price and it is 100% while $181.35 is sold price and it is a profit, which percent we need to calculate:
$155 : 100% = $181.35 : x
x = $181.35 · 100% ÷ $155
x = 117%
The percent profit is difference between sold and cost price percent:
117% - 100% = 17%
Therefore, the percent profit made by the owner is 17%.
