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最小的五位数 = nombor lima digit paling kecil 五位数有万、千、百、十、个五个数位。要最小，最高的万位放最小的非零数字，其余每一位都放最小的数字。 例子：最小的三位数是 100，最小的四位数是 1 000。 注意：最高位不能是 0，不然就不是五位数了。

smallest five-digit number = nombor lima digit paling kecil A five-digit number has five places: ten thousands, thousands, hundreds, tens and ones. To make it as small as possible, put the smallest non-zero digit in the highest place and the smallest digit in every other place. Example: the smallest three-digit number is 100 and the smallest four-digit number is 1 000. Watch out: the highest place cannot be 0, or the number would not have five digits.

估计后验证 = anggar, kemudian uji 乘数 31 大约是 30。想一想 30 要乘大约多少才到一万，就知道三位数的百位大概要放几。选出一两个接近的数字，把整个三位数写出来和 31 相乘，看积有没有到五位数。 例子：□40 × 18，试 540 × 18 = 9 720 不够，640 × 18 = 11 520 够了，所以 □ 最小是 6。 注意：差一点点到一万也不行，一定要算出准确的积来比较。

estimate, then test = anggar, kemudian uji The multiplier 31 is about 30. Think about roughly what 30 must be multiplied by to reach ten thousand; that tells you about which hundreds digit is needed. Pick one or two close digits, write the whole three-digit number and multiply by 31 to see whether the product has five digits. Example: □40 × 18: 540 × 18 = 9 720 is not enough, 640 × 18 = 11 520 is, so the smallest □ is 6. Watch out: just below ten thousand is still not enough; always work out the exact product.

为什么要试小的 = mengapa uji digit kecil 题目问的是“最小”的数字。找到一个能让积成为五位数的数字，只说明它“可以”，还不能说明它“最小”。想一想：怎样才能肯定没有更小的数字也可以？ 例子：一个数字谜题里，7 可以，6 也可以，5 不可以，那么最小的是 6，而不是一开始找到的 7。 注意：“可以”和“最小”是两件不同的事。

why test smaller digits = mengapa uji digit kecil The question asks for the smallest digit. Finding a digit that makes a five-digit product only shows that it works; it does not show that it is the smallest. Think: how can you be sure that no smaller digit works too? Example: in a digit puzzle, 7 works, 6 works and 5 does not, so the smallest is 6, not the 7 found first. Watch out: works and smallest are two different ideas.