22．（本小题10分）为了能有效地使用电力资源，我市实行居民峰谷用电，居民家庭在峰时段（上午8：00～晚上21：00）用

来源：学生作业帮编辑：搜搜考试网作业帮分类：数学作业时间：2024/06/05 11:18:12

22．（本小题10分）为了能有效地使用电力资源，我市实行居民峰谷用电，居民家庭在峰时段（上午8：00～晚上21：00）用电的电价为0.55元/千瓦时；谷时段（晚上21：00～次日晨8：00）用电的电价为0.30元/千瓦时．若某居民户2月份用电100千瓦时，其中谷时段用电x千瓦时，应缴纳电费y元．（1）请用含x的代数式表示y；（2）若该居民户2月份谷时段用电40千瓦时，求该居民户这个月应缴纳电费．（3）若该居民户2月份缴纳电费为40元，求该居民户峰时段用电多少千瓦时．
22．（本小题10分）为了能有效地使用电力资源，我市实行居民峰谷

解题思路： 22. （1）y=0.30x+（100－x）×0.55=－0.25x+55；··················································· 3分（2）当x=40时，y=－0.25x+55=45元；························································· 5分（3）当y=40时，－0.25x+55=40，解得x=60，················································· 7分 ∴100－x=40千瓦时． ∴该居民户峰时段用电40千瓦时．······························································· 8分
解题过程：
22.
（1）y=0.30x+（100－x）×0.55=－0.25x+55；··················································· 3分
（2）当x=40时，y=－0.25x+55=45元；························································· 5分
（3）当y=40时，－0.25x+55=40，解得x=60，················································· 7分
∴100－x=40千瓦时．
∴该居民户峰时段用电40千瓦时．······························································· 8分
最终答案：22. （1）y=0.30x+（100－x）×0.55=－0.25x+55；··················································· 3分（2）当x=40时，y=－0.25x+55=45元；························································· 5分（3）当y=40时，－0.25x+55=40，解得x=60，················································· 7分 ∴100－x=40千瓦时． ∴该居民户峰时段用电40千瓦时．······························································· 8分