Out of total capital required to start a business A invested 30%, B invested $$\frac{2}{5}$$ th and C invested the remaining capital. At the end of one year sum of Rs. 4000 is earned as a profit which is 20% of the capital given by B, then find how much C invested in the business ?

Total profit = Rs. 4000
According to the question,
$$\eqalign{ & {\text{20% of B's capital}} = {\text{Rs}}{\text{.}}\,{\text{4000}} \cr & {\text{1% of B's capital}} = {\text{Rs}}{\text{.}}\,\frac{{{\text{4000}}}}{{20}} \cr & {\text{B's total capital}} \cr & = {\text{Rs}}{\text{. }}\frac{{{\text{4000}}}}{{20}} \times 100 \cr & = {\text{Rs}}{\text{. }}20000 \cr} $$
Let total capital required for business = 100 units.

	A	:	B	:	C
Capital	30	:	40	:	30
	× 500	:	× 500	:	× 500
	15000	:	20000	:	$$\boxed{15000}$$

Hence, Required capital for C = Rs. 15000