Heather's water heater needs repair.The plumber says it will cost $300 to fix the unit,which currently costs $75 per year to operate.Or Heather could buy a new water heater for $500,including installation and the new heated would save 60% on annual opearating costs.How long would it take for the new unit to pay for itself?
问题描述：
Heather's water heater needs repair.The plumber says it will cost $300 to fix the unit,which currently costs $75 per year to operate.Or Heather could buy a new water heater for $500,including installation and the new heated would save 60% on annual opearating costs.How long would it take for the new unit to pay for itself?
答
希瑟的热水器需要修复。 水管工说，它将耗资300元修复单位，目前成本75元，每年运作。 或希瑟500元可以买一个新的热水器，包括安装和新的加热年度opearating成本节省60。 新单位的需要多久来支付本身？
不会！
答
Assume it takes n years:In the case of having it repaired, in n years, the total cost would be: 300 + 75n dollarsIn the case of buying a new one, in n years, the total cost would be: 500 + 75(1-60%)n ...