IN HOW MANY WHOLE NUMBERS LESS THAN 100 DOES THE DIGIT 9 APPEAR AT LEAST ONCE?
To determine the number of whole numbers less than 100 in which the digit 9 appears at least once, you can go through all the numbers between 1 and 99 and count the ones that contain the digit 9.
Here's how you can approach it:
1. Start with a counter set to zero.
2. Iterate through all the numbers between 1 and 99.
3. For each number, check if it contains the digit 9. You can do this by converting the number to a string and using the 'in' operator to check if '9' is present in the string.
4. If the digit 9 is found, increment the counter by 1.
5. After checking all the numbers, the final value of the counter will give you the total count of whole numbers less than 100 in which the digit 9 appears at least once.
Alternatively, you can use a more mathematical approach to solve this problem. Since there are 10 digits (0 to 9), and each digit appears the same number of times in its place value, you know that each digit appears in 1/10th of the numbers. Therefore, the digit 9 will appear in 1/10th of the numbers. Since you have 99 numbers, you can calculate 1/10th of 99 to find the approximate count.
Using the first method:
1. Initialize the counter to zero.
2. Iterate through the numbers from 1 to 99.
3. For each number, convert it to a string and check if '9' is in the string.
4. If '9' is found, increment the counter by 1.
5. After checking all the numbers, you will find that the digit 9 appears in 20 whole numbers less than 100.
Using the second method:
1. Divide 99 by 10 to get 9.9.
2. Round down the result to the nearest whole number, which gives you 9.
3. Therefore, the digit 9 appears in approximately 9 whole numbers less than 100.
So, based on the two methods, the digit 9 appears in 20 whole numbers less than 100.