A hardware store owner bought a used refrigerator for $155 and marked it to sell for a profit of 30% on the cost. He then sold it for 10% less than the marked price. What is the percent profit made by the owner?

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%.

Original Cost : $155

Marked Price : 155 * 1.30 = $201.5

Sold price : $201.50 - (0.10*201.50) = $181.35

Profit (%) = (181.35/155) * 100=117%

So, there is 17% increase in the original price. so he earned 17% profit.