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本帖最后由 Yike 于 2019-11-28 21:59 编辑
月亮 发表于 2019-11-26 18:06 
这种题是凑出来的吗
John is one year older than his wife Mary. They have three children,
whose ages are two years apart.
The product of John and Mary’s ages is less than 2019. The product
of the three children’s ages is also less than 2019.
Next year both these products will be greater than 2020.
This year, what is the sum of all five ages?
今天仔细回忆了一下,小朋友当时是这样做的:
(1)John和Mary之相差一岁,选择通过平方数来缩小范围 。
- 40 X 40 = 1600
- 50 X 50 = 2500
- 选择计算45 X 45,结果为2025,比题目限定的2019大,
- 试算 44 X 45,结果为1980,符合题目要求;
- 再计算45 X46,结果为2070,符合题目要求
所以John是45岁,Mary是44岁
(2)孩子是相差2岁,选择通过立方数来缩小范围(大概在10~15)
- 凭感觉选择了12,结果为1728,似乎满足条件
- 试算10 X 12 X 14,结果为1680,满足条件
- 试算11 X 13 X 15, 结果为2145,满足条件
所以结果为45+44+10+12+14= 125。
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