SOLUTION: QUESTION: SOME TREE-DIGIT NUMBERS, SUCH AS 101 AND 313, READ THE SAME FORWARD AND BACKWARD, IF YOU SELECT A NUMBER FROM ALL THREE-DIGIT NUMBERS, FIND THE PROBABILITY THAT IT WILL R

Algebra ->  Probability-and-statistics -> SOLUTION: QUESTION: SOME TREE-DIGIT NUMBERS, SUCH AS 101 AND 313, READ THE SAME FORWARD AND BACKWARD, IF YOU SELECT A NUMBER FROM ALL THREE-DIGIT NUMBERS, FIND THE PROBABILITY THAT IT WILL R      Log On


   

Question 752387: QUESTION: SOME TREE-DIGIT NUMBERS, SUCH AS 101 AND 313, READ THE SAME FORWARD AND BACKWARD, IF YOU SELECT A NUMBER FROM ALL THREE-DIGIT NUMBERS, FIND THE PROBABILITY THAT IT WILL READ THE SAME FORWARD AND BACKWARD...?
Found 2 solutions by AnlytcPhil, Edwin McCravy:
Answer by AnlytcPhil(1807) About Me  (Show Source):
You can put this solution on YOUR website!
Such numbers as 101 AND 313 are called "palindromes".

Such numbers are of the form ABA

There are 10 digits but since we cannot choose 0
for the first digit in a 3-digit number, we can only 
choose one of the other 9 digits for the A.  For each
of those 9 ways to choose A, we can choose the B in
10 ways because 0 CAN be chosen for the middle digit B. 

So that's 9x10 wars or 90 ways

Edwin

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
9 ways to choose the digit to go 1st and 3rd. (can't choose 0 for a 1st digit)
10 ways to choose the middle digit. (can choose 0 for the middle digit)
10×9 = 90 ways