Question

若在一个两位数后添上数字 $1$ ，这个两位数的十位数字为 $t$ ，个位数字为 $u$ ，则新数为：

If the digit $1$ is placed after a two digit number whose tens’ digit is $t,$ and units’ digit is $u,$ the new number is:

$10t+u+1$

$100t+10u+1$

$1000t+10u+1$

$t+u+1$

以上答案均不正确

None of these answers

知识点：位值数字

原来的两位数是 $10t+u$

The original two digit number is $10t+u$

在末尾添上一位数字，要先将原数乘以 $10$ ，再加上该数字

Appending a digit multiplies the original number by $10$ before adding that digit

这个两位数是 $10t+u$ 。在它后面添上 $1$ ，得到 $\begin{aligned} &10(10t+u)+1\\ &=100t+10u+1 \end{aligned}\text{。}$

因此，正确答案是 B。

The two digit number is $10t+u.$ Placing $1$ after it produces $\begin{aligned} &10(10t+u)+1\\ &=100t+10u+1. \end{aligned}$

Thus, the correct answer is B.