The master and apprentice work together to make a batch of parts. The master makes an average of 15 parts per hour, and the apprentice makes 8 parts per hour, which can be completed in 6 hours. How many parts are there in total?
师徒两人合作一批零件，师傅平均每小时做15个，徒弟每小时做8个，6小时可以完成．这批零件一共有多少个？
<gadget id="calculator">15 + 8</gadget>
<output>23</output>

<gadget id="calculator">23 * 6</gadget>
<output>138</output>

<result>138</result>