This maths question is really bugging me. In my Active Maths Book 1 pg 116 question 13, there is a question on palindromic numbers. I understand the term palindromic and got my first answer to part (i) which asked me the amount of 3 digit palindromic number ...my answer is 90 ...now it asks me to find the number of palindromic numbers between 10 to the power of 6 and 10 to the power of 7.
I know from the back of the book that the answer is supposed to be 9000 but when i try the question i get a different answer. Andyone know how to do it?
(i) 9x10x1 = 90
(ii)10^6 = 1000000
10^7 = 10000000
therefore 9 x 10 x 10 x 10 x 1 x 1 x 1 = 9000
Hope that helps
Michaels is correct,
10^6 is a seven digit number and 10^7 is an eight digit number so all the numbers in between are 7 digit numbers.
9 choices (1-9) for the first digit, which means 1 for the seventh (as it has to be the same)
10 choices (0-9) for the second digit, which means 1 for the sixth (as it as to be the same)
10 choices (0-9) for the third digit, which means 1 for the fifth (as it as to be the same)
10 choices (0-9) for the fourth digit.
So thats where you get
9 x 10 x 10 x 10 x 1 x 1 x 1 = 9,000