IMAT 2012 Q5 [Water]

The volume of water expands by 9% when it freezes.

If you want a block of ice 40 {cm^3}, how much water would you need to put into a freezer?

A. 36.7 {cm^3}
B. 38.2 {cm^3}
C. 38.0 {cm^3}
D. 40.0 {cm^3}
E. 37.0 {cm^3}

Lets mark the volume of water x as 100%, and y as volume of ice.

It is said that the volume expands by 9% when it freezes, meaning that the volume of the ice is given as 100% (water) + 9% expansion. In total the volume of ice is equivalent to 109% of the water volume.

Having this in mind, we can make an equation: y = 109%x \to y= \frac{109}{100} x \to x=\frac{100}{109}y = \frac{100}{109} 40cm^3 \to x=36.697cm^3 \sim 36.7cm^3.

Which is the answer to this question.

P.s. If you didn’t know % is equivalent to \frac{1}{100}