Master Zhang buys some apples at the price of 3 apples for 1 yuan, and sells these apples at the price of 5 apples for 2 yuan. If he wants to make a profit of 10 yuan, how many apples must he sell? ．
张师傅以1元钱3个苹果的价格买苹果若干个，又以2元钱5个苹果的价格将这些苹果卖出，如果他要赚得10元钱利润，那么他必须卖出苹果多少个．
<gadget id="calculator">6 - 5</gadget>
<output>1</output>

<gadget id="calculator">10 / 1</gadget>
<output>10</output>

<gadget id="calculator">10 * 15</gadget>
<output>150</output>

<result>150</result>