Question

In an alloy ratio of Cu and Zn is 4:3. when 4 kg Zn is mixed into that alloy then the ratio of Cu and Zn becomes 6:5. Find the initial amount
of Zn
A 50 kg
B.36 kg
C 48 kg
D None​

Answer 1

The initial amount of Zn is 36 kg, Option B.

Given, In an alloy ratio of Cu and Zn is 4:3

Let the quantity of Cu = 4x

Let the quantity of Zn = 3x

If 4kg of Zn is mixed into the alloy then,

⇒ Quantity of Zn = 3x + 4

⇒ Quantity of Cu = 4x

Ratio = 4x : 3x + 4

According to the question, The ratio is 6 : 5

So,

$\frac{4x}{3x + 4} = \frac{6}{5} \\ \\ 20x = 6(3x + 4) \\ \\ 20x = 18x + 24 \\ \\ 2x = 24 \\ \\ x = 12$

Initial amount of Zn = 3 x = 3 × 12 = 36 kg.

Therefore, The initial amount of Zn is 36 kg, Option B.