AMC 8 1988 Problem 10

AMC8 1988 年第 10 题

余数与同余★★☆☆☆

Chris' birthday is on a Thursday this year. What day of the week will it be 60 days after her birthday?

今年 Chris 的生日在周四。她生日后的第 60 天是周几？

正确答案 · Correct Answer

解析 · Solution

Solution 1

Since 60 days is 8 weeks and 4 days, the day 60 days after Chris' birthday will be 4 days after a Thursday, which is

\text{Monday}

Since

60\equiv4\pmod7

, the day 60 days after Chris' birthday will be 4 days after a Thursday, which is

\text{Monday}

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