Hello. I am stuck with this question and have no idea how to start it. Here it is:
A palindromic number is one which reads the same backwards as forwards.
(a) Find a three-digit palindromic number which is exactly 19 times the
sum of its digits.
(b) Find all four-digit palindromic numbers which are exactly 352 times
the sum of their digits.
Thanks!
(a) A 3-digit palindrome will have the same hundreds and units digits
Let hundreds/units and tens digits be H, and M, respectively
Then the number is: 100H + 10M + H
Since the number is 19 times the sum of its digits, we get: 100H + 10M + H = 19(H + M + H)
101H + 10M = 19(2H + M)
101H + 10M = 38H + 19M
101H - 38H = 19M - 10M
63H = 9M =====>
M is a DIGIT, so H, or hundreds/units digit can ONLY be 1. Therefore, M = 7(1) = 7
(b) A 4-digit palindrome will have the same thousands and units digits, and the same hundreds and tens digits
Let thousands/units and hundreds/tens digits be T, and H, respectively
Then the number is: 1,000T + 100H + 10H + T, or 1,001T + 110H
Since the number is 352 times the sum of its digits, we get: 1,001T + 110H = 352(T + H + H + T)
1,001T + 110H = 352(2T + 2H)
1,001T + 110H = 704T + 704H
1,001T - 704T = 704H - 110H
297T = 594H =====>
H is a DIGIT, and can ONLY be 1, 2, 3, or 4. Therefore: