According to the question.
([P + (P x 6 x T)/100] - [P + (P x 1 x T)/100] = 600 - 200
⇒ 5PT/100 = 400
⇒ PT = 8000
Again, for 6% rate,
SI = PTR/100 = (8000 x 6)/100 = ₹ 480
∴ Sum = 600 - 480 = ₹ 120
As we have, PT = 8000
∴ T = 8000/120 = 200/3 = 662/3 yr