Posted by Please help me understand on Thursday, February 9, 2012 at 1:39am.
Yes it was answered previously but I am sorry that I did not follow the pattern. I was told that the answer that I submitted was incorrect. Please help if you can. Thank you so very much.
THE PROBLEM READS:
A three-digit number increases by 9 if we exchange the second and third digits. The same three-digit number increases by 90 if we exchange the first and second digits. By how much will the value increase if we exchange the first and third digits?
- Math Help - Reiny, Thursday, February 9, 2012 at 8:17am
in the original number,
let the unit digit be a,
the tens digit be b
and the hundred digit be c
the appearance of our number is cba
then the value of our number is 100c + 10b + a
case1: interchange 2nd and 3rd digit
number looks like cab
value of our new number is 100c + 10a + b
so 100c + 10a + b - (100c + 10b + a) = 9
9a -9b = 9
a-b = 1 , (#1)
case2: interchange the 1st and 2nd digit
appearance of new number is bca
value of new number is 100b + 10c + a
so 100b+ 10c + a - (100c + 10b + a) = 90
90b -90c = 90
b - c = 1 , (#2)
case3: interchange 1st and 3rd
appearance of new number is abc
value of new number is 100a + 10b + c
change in value = 100a + 10b + c - (100c + 10b + a)
= 99a - 99c
but if we add #1 and #2
a - c = 2
so 99(a-c) = 99(2) = 198
A little know feature of the above is the following "math trick"
1. Pick any 3 digit number, all different and the hundreds digit greater than the unit digit
2. reverse the digits and subtract the numbers. If you get a 2 digit result, insert a 0 in the hundred place
3. reverse your subtraction answer and add the last two results,
4. You will always get 1089
Answer this Question
More Related Questions
- Elementary Satistics - Test the following function to determine whether it is a ...
- math answer check - x is a binomial random variable. (Give your answers correct ...
- statistics - Can someone please tell me how I miss this, I added them up 29 and ...
- math - Can someone please help me on these I have look at the examples and done ...
- math help - Use the following table to answer the questions. (Give your answers ...
- Math - Please help me with the following problem, I have submitted the answer: ...
- Math - Does studying for an exam pay off? The number of hours studied, x, is ...
- Math PLEASE help - Does studying for an exam pay off? The number of hours ...
- physics - Vector V1 is 8.58 units long and points along the -x axis. Vector V2 ...
- Math Challenge - Please help if can with the following problem, I have submitted...