batch of water pipes was transported to the construction site, and the administrator piled the water pipes into 3 piles with 21 pipes in each pile, and there were 7 pipes left. How many pipes are there in this batch?
建筑工地运到一批水管，管理员把这批水管按每堆21根堆成3堆后，还剩7根．问这批水管有多少根？
<gadget id="calculator">21 * 3</gadget>
<output>63</output>

<gadget id="calculator">63 + 7</gadget>
<output>70</output>

<result>70</result>