Find the 3-digit number which satisfies the following conditions.
The number is a multiple of 4.
The reverse of the 3-digit number is 495 greater than the number itself.
If you add 36 to the number, the tens and ones digit will swap with each other.
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Let the 3 -digit number be X Y Z = 1 0 0 X + 1 0 Y + Z for single digit numbers X , Y , and Z .
Since adding 3 6 to the number make the tens and ones digit will swap with each other, 1 0 Y + Z + 3 6 = 1 0 Z + Y , which solves to Z = Y + 4 . Since Y and Z are single digits, the possibilities for ( Y , Z ) are ( 0 , 4 ) , ( 1 , 5 ) , ( 2 , 6 ) , ( 3 , 7 ) , ( 4 , 8 ) , and ( 5 , 9 ) .
Since 1 0 0 X + 1 0 Y + Z is a multiple of 4 , and 1 0 0 X is a multiple of 4 , 1 0 Y + Z must also be a multiple of 4 . The possibilites for ( Y , Z ) are now further limited to ( 0 , 4 ) and ( 4 , 8 ) .
Since the reverse of the 3 -digit number is 4 9 5 greater than the number itself, 1 0 0 X + 1 0 Y + Z + 4 9 5 = 1 0 0 Z + 1 0 Y + X , which solves to Z = X + 5 , so Z ≥ 5 . The possibilites for ( Y , Z ) is now limited to ( 4 , 8 ) , which makes X = 3 , Y = 4 , and Z = 8 for the number 3 4 8 .