Explanation:

Let the maximum marks be x.
Given, Swati secure 40% marks and failed by 60 marks while Kriti secured 60% marks and passed by 40% marks.
∴  Putting the given info in the eq. form,
we get pass marks = (40% of x) + 60 = (60% of x) – 40
⇒   (60% of x) – (40% of x) = 60 + 40
⇒   20% of x = 100
⇒   x = 500
∴  Maximum marks = 500
Now, Chitra secured 80 marks more than the pass marks.
∴  Chitra scored = (40% of x) + 60 + 80
= 40/100 × 500 + 140  = 340 marks
Now,  Required percentage = 340 x 500 /100 = 68%