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% ?

Solution (By Examveda Team)

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