50% of a = b, then b% of 40 is the same as _________ of a.

$ \large \frac{50}{100} \times a = b$

$ \large \frac{a}{2} = b$

Now we have to find $ \large b % $ of $ \large 40$

$ \large = \frac{b}{100} \times 40 = \frac{a}{200} \times 40$

$ \large = \frac{a}{5}$

$ \large = 0.2a$