A four-digit number gets reversed when it is multiplied by 4. find the sum of the digits of the number.

Let the number be 'abcd'.
We can write as 1000a+100b+10c+d.
According to the question:
(1000a+100b+10c+d)x4=1000d+100c+10b+a
We get as 3999a+390b-60c-996d=0
Use hit and trial :
Take a=2,b=1,c=7,d=8.The above condition gets satisfied.
Now add the values of a,b,c,d.That will be your answer.
Answer:18