What is formula for depreciation rate as per wdv method?

In financial reporting module [2014 edition] pg 1.65 the formula given is Depreciation rate=(1/n) x(Residual Value/Cost of Asset)x100 n=useful life Another formula I have frequently come across in other authors books is Depreciation rate = 1-(Residual Value/Cost of Asset)^(1/n) Which one should be followed for CA Final November 2014 Exams?

Whether previous W D V method has been changed. Like earlier we are charging rate of depreciation on the written down value of the asset. Please clear me what is the change.