The chemical fertilizer plant saved an average of 7 tons of water per day in April, May, and June. How many tons of water were saved in these three months?
化肥厂四、五、六月3个月平均每天节约用水7吨，这三个月份共节约用水多少吨？
<gadget id="calculator">30 + 31 + 30</gadget>
<output>91</output>

<gadget id="calculator">7 * 91</gadget>
<output>637</output>

<result>637</result>