Question

Lucius 正在每次减 $7$ 倒着数。他的前三个数是 $100$ 、 $93$ 、 $86$ 。他的第 $10$ 个数是多少？

Lucius is counting backward by $7$ s. His first three numbers are $100,$ $93,$ and $86.$ What is his $10$ th number?

$30$

$37$

$42$

$44$

$47$

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从第一个数到第十个数之间有 $10 - 1 = 9$ 个间隔。第一个数是 $100$ ，第 $10$ 个数前要每次减 $7$ 。

因此总共减去 $9 \times 7 = 63$ ，从 $100$ 剩下 $100 - 63 = 37$ ，选 B。

There will be $10 - 1 = 9$ gaps between his first number $100$ and his $10$ th number. Each gap has size $7.$

So, he will subtract a total of $9 \times 7 = 63$ from $100,$ leaving an answer of $100 - 63 = 37,$ which is choice B.