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Question 649550: Find a 4 digit number such that the number formed by reversing the digits is 4 times its original number?
Answer by swincher4391(1107)   (Show Source):
You can put this solution on YOUR website! We know that D must be even because 4D = A. A has to be 2 since A*4 + any thing we carry from the hundreds gives a number less than 10. So D could be 8 or 9. D must be 8 because 8*4 ends in 2 and 9*4 does not.
B*4 gives us a number less than 10 since there is no carry figure to the thousands. B must be different than A, so B must be 1. We have found that A=2 B = 1 D = 8. We know that 21C8 * 4 = 8C12. When we take C and multiply it by 4 and add 3 ( since 8*4 = 32) we get 7. Which is C.
Thus the number is 2178.
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