The speed of light is approximately meters per second. How many seconds will it take for light to travel the meters from Earth to the Sun?
Solution to yesterday’s problem:
We can use the blanks method to solve this problem. Since we’re concerned with three-digit numbers, let’s set up three blanks:
____ ____ ____
In the first blank, there can be any digit except zero (then it would be a two-digit number). That’s 9 possibilities.
__9__ ____ ____
In the second blank, there can be any digit 0-9.
__9__ __10__ ____
In the third blank, however, there can only be one digit possible. This is because in order for the number to be a palindrome, the first digit and the last digit must be the same.
__9__ __10__ __1__
Multiplying these numbers, we find that there are 90 three-digit palindromes in all.