Question

640 mL of a mixture contains milk and water in ratio 6 : 2. How much of the water is to be added to get a new mixture containing half milk and half water?
A. 360 mL
B. 320 mL
C. 310 mL
D. 330 mL

Answer 1

Hint: The total mixture of milk and water is given to us. We have to make a new mixture of milk and water in which we have to add the quantity of water so that the ratio becomes 6:6 that is the equal ratio of both milk and water.

Complete step by step answer:
-It is given to us that the total quantity of the mixture is 640 mL in which the ratio of milk and water is 6:2.
-Now, we have to add some quantity of water in the mixture so that the ratio of the milk and water becomes 6:6.
-Also, we can observe that the concentration of water is 4 times less than the concentration of the milk.
-Now, we know that the total quantity is 640 mL that is
-Quantity of milk + quantity of water = 640 mL ….. (1)
-Let the ratio of the product = x
-So, according to the question, the quantity of milk = 6x
-And the quantity of water = 2x.
-So, from equation (1) we will get,
\[\begin{align}
  & \text{6x + 2x = 640} \\
 & \text{8x = 640} \\
 & \text{x = 80} \\
\end{align}\]

-Hence, the quantity of the milk will be $\text{6x = 6 }\times \text{ 80 = 480 mL}$ and the quantity of water will be $\text{2x = 2 }\times \text{ 80 = 160 mL}$
-Now, to calculate the equal amount of water we will subtract:
480 - 160 = 320 mL.
So, the correct answer is “Option B”.

Note: Water consists of an equal ratio of hydrogen and oxygen no matter from where it comes because it follows the law of constant proportion according to which the compound always consists of an equal ratio of the elements.