Question

In the question given below, use the following notations :

A " B means 'add B to A';

A ' B means 'subtract B from A';

A @ B means 'divide A by B';

A ★ B means 'multiply A by B';

Now, answer the following question.

The time taken by two running trains in crossing each other is calculated by dividing the sum of the lengths of two trains by the total speed of the two trains. If the length of the first train is $L_1$, the length of the second train is $L_2$, the speed of the first train is $V_1$ and the speed of the second train is $V_2$, which of the following expressions would represent the time taken ?

• A. ($L_1$ "$L_2$) $★$ ($V_1$ "$V_2$)
• B. ($L_1$ "$L_2$) @ ($V_1$ "$V_2$)
• C. [($L_1$ "$L_2$) @ ($V_1$ "$V_2$)] $★$ 60
• D. ($L_1$ '$L_2$) @ ($V_1$ '$V_2$)

Answer 1

The correct option is B ($L_1$ "$L_2$) @ ($V_1$ "$V_2$)

Given that:

Length of two train = $L_1$ and $L_2$
Speed of the train = $V_1$ and $V_2$
Then time taken to cross each other = $\frac{L_1+L_2}{V_1+V_2}$
Exchange the sign according to the question then
($L_1$ "$L_2$) @ ($V_1$ "$V_2$)
Hence option B is answer.