Question

A large tank contains 1 liter of water. A pipe is connected to the tank, which fills the tank at a rate of 3 liters per minute. Find the time required to fill the tank with 14.5 liters of water.

• A. 5.5 min
• B. 6 min
• C. 5 min
• D. 4.5 min

Answer 1

The correct option is D 4.5 min

Let the time taken to fill the tank be $x$ min.
Rate of water coming from the pipe = 3 L per min

Quantity of water filled in $x$ minutes
$=3\times x=3x$

Quantity of water present in the tank initially = 1 L
Quantity of water in the tank after $x$ minutes = $3x+1$
$\Rightarrow f\left(x\right)=3x+1$

We need to find the time, $x$, for the quantity of water $f\left(x\right)=14.5$
Let’s substitute $f\left(x\right)$ in the above equation.
$\Rightarrow 14.5=3x+1$
$\Rightarrow 3x=14.5-1$
$\Rightarrow 3x=13.5$
$\Rightarrow x=\frac{13.5}{3}$
$\Rightarrow x=4.5$ min

Hence, 4.5 min will be required to fill the tank with 14.5 L of water.