The total amount of money obtained from selling 5 pieces of a commodity at a profit of 10 yuan each is equal to the total amount of money obtained from selling 4 pieces at a profit of 25 yuan each. What is the purchase price of each commodity.
某商品按每个10元的利润卖出5个所得的总钱数，与按每个25元的利润卖出4个的总钱数相等，这种商品每个进价是多少元．
<gadget id="calculator">25 * 4</gadget>
<output>100</output>

<gadget id="calculator">10 * 5</gadget>
<output>50</output>

<gadget id="calculator">100 - 50</gadget>
<output>50</output>

<gadget id="calculator">5 - 4</gadget>
<output>1</output>

<gadget id="calculator">50 / 1</gadget>
<output>50</output>

<result>50</result>