一條關於Significant Figures既問題（英文數）

2007-08-17 5:48 am

Given a four-digit odd number which is greater than 9000 and is divisible by 13.
When rounded off to 3 significant figures, it is divisible by 4.
When rounded off to 2 significant figures, it is divisible by 11
Find the number.

回答 (1)

[匿名]

2007-08-17 6:15 am

✔ 最佳答案

1. 由於題目需要4位數, 而要greater than 9000
所以個數1定係9000 至 9999之間

2. When rounded off to 2 significant figures, it is divisible by 11
9X00 之中只有 9900整除11 (X 係0-9)
因為rounded off to 2 significant figures要係9900
所以個數必在 9850 - 9949之間

3. 係9850 - 9949之間而又divisible by 13
就只有9854, 9867, 9880, 9893, 9906, 9919, 9932, 9945 呢8個

4. 而以上個8個數當rounded off to 3 significant figures, it is divisible by 4
就得番 9880, 9919

Ans有2個: 9880, 9919

參考: myself

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