In 2 kg mixture of copper and aluminium, 30% is copper. How much aluminium powder should be added to the mixture so that the quantity of copper becomes 20% ?

Answer: Option C

According to the question,
Mixture of copper and aluminium = 2000 gms
30% is copper means
= $$\frac{30}{100}$$ × 2000
= 600 gms copper
$$\begin{array}{rl}& \Rightarrow \frac{600}{1400+x}=\frac{20\%}{80\%}\\ & \Rightarrow 1400+x=2400\end{array}$$
⇒ x = 1000 gms