There are 90 households in 7 buildings, and each household saves 1 ton of water a month. After one year, how many tons of water are saved by the residents of these 7 buildings?
7栋楼共有90户人家，每户人家一个月节约用水1吨，一年下来，这7栋楼的住户共节约多少吨水．
<gadget id="calculator">1 * 12 * 90</gadget>
<output>1_080</output>

<result>1_080</result>