If 30% of A is added to 40% of B, the answer is 80% of B. What percentage of A is B ?

Answer: Option D

According to the question,
$$\frac{30A}{100}$$ + $$\frac{40B}{100}$$
= $$\frac{80B}{100}$$
30A = 40B
⇒ 3A = 4B
⇒ A = $$\frac{4B}{3}$$
Required % = $$\frac{B}{A}$$ × 100
= $$\frac{B\times 3}{4B}$$ × 100
= 75%