Question

Some four​-digit ​numbers, such as 3003 and 6226​, read the same forward and backward. If a boy selects a number from all four​-digit ​numbers, find the probability that it will read the same forward and backward.

Answer 1

Answer:

The probability of selecting such number =$\frac{90}{9000} = \frac{1}{100}$

Explanation:

4-digit numbers start from 1000 and ends at 9999

So, there are 9000 4-digit numbers present

There are 90 palindrome numbers (which reads the same forward and backward) present between 1000-9999. They are 1001; 1111; 1221; 1331; ... 1001; 1111; 1221; 1331; ... to 9669; 9779; 9889; 9999; 9669; 9779; 9889; 9999

Therefore, the probability of selecting such number =$\frac{90}{9000} = \frac{1}{100}$