Question

Jessica fills a cube shaped tank that has an edge of 70 cm with water from a tap. Water flows into the tank at a rate of 7L per minute. How long will it take to fill the tank fully?

Answer 1

The volume of the tank is (70 cm)³ = 343,000 cm³.

Now,

1 mL = 1 cm³

1 L = 1000 mL

so we convert the given rate to

$\dfrac{7\,\rm L}{1\,\rm min} \cdot \dfrac{1000\,\rm mL}{1\,\rm L} \cdot \dfrac{1\,\mathrm{cm}^3}{1\,\rm mL} = \dfrac{7000\,\mathrm{cm}^3}{1\,\rm min}$

Then the time it will take to fill up the tank is

$343,000\,\mathrm{cm}^3 \cdot \dfrac{1\,\rm min}{7000\,\mathrm{cm}^3} = \boxed{49\,\rm min}$