Question

There are 90 litres castrol and 150 litres CRB mobil oils. The price of castrol is Rs. 80 per litre and price of CRB is Rs. 75 per litre. Equal amount of castrol and CRB is taken out and then CRB is poured out in the vessel of castrol and castrol is poured out in the vessel of CRB. Now the ratio of both the mixtures is same. What is the amount of mobil oil taken out from each of the vessel?

• A. 45 litres
• B. 56.25 litres
• C. 24.5 litres
• D. 36 litres

Answer 1

The correct option is B 56.25 litres

Let 'x' litres be the amount taken out from both the vessel.
Then we get the required equation as:
$\frac{Castrol}{CRB}=\frac{90-x}{x}=\frac{x}{150-x}$
Check for different values of x from options.
We find that x = 56.25 litres satisfy the above equation.
Hence, option (b) is the correct answer.

Alternate Approach:
Note in this type of question individual prices does not matter. To prove this solve it algebraically.
Exchanged amount =
$\frac{3\times 150+5\times 90}{2(3+5)}=\frac{450}{8}=56.25litre$
Here, 3 and 5 are obtainded from the ratio of amounts i.e, from 90 and 150.