Here’s a fun
math puzzle involving percents. The solution
is not terribly difficult – but it is surprising how many people end up getting
the answer wrong. Why not give it a try:

**The owner of a farm stand puts a bunch of watermelons on display at the beginning of the day. The watermelons have a mass of 200 kg. 99% of the watermelons’ mass is water. It is hot, and during the day water evaporates from the melons. At the end of the day, 98% of the watermelons’ mass is water. Assuming that no watermelons were sold during the day, what is the mass of the watermelons at the end of the day?**

If you’d
like to check your answer, the correct solution is below.

If you’re
having a hard time, consider this puzzle. The math involved the same as the watermelon
problem, but the way in which the puzzle is presented tends to make the
solution easier to find.

**Some guys planned a New Years’ party and invited only women. At the party, there were a total of 200 people, 99% of whom were women. A lot of the women thought that the party was lame, so they left. After one hour, 98% of the people left at the party were women. How many total people were at the party after one hour?**

This puzzle
is slightly easier to grasp because it explicitly states that there are men and
women. (And, it states that only women
leave the party.)

See below for the solutions.

__Solution: New Years’ party puzzle__

It’s not
very hard to determine how many men and women there were at the beginning of
the party:

Women: 99% of 200 = 198 Men: 1% of 200 = 2

Since only women
left the party, there are still two men after one hour. However, these two men now comprise 2% of the
total party crowd. 2 is 2% of 100…
therefore, there are 100 people at the party after one hour.

__Solution: Watermelon puzzle__

The watermelon puzzle is a little trickier simply because the problem doesn’t explicitly state that the watermelon is made up of water and solids. Therefore, many people get hung up focusing on the water.

If 99% of
the watermelon mass is water, then 1% is made up of solids. 1% of 200kg is 2 kg – so there are 2 kg of
solids. Solids do not evaporate, so at
the end of the day, there are still 2 kg of solids. This now comprises 2% of the total watermelon
mass. 2 kg is 2% of 100 kg. Therefore, there are 100 kg of watermelons
left at the end of the day.

Happy New
Years’, Everyone!

------------------------------

For Math Tutorials and Silly Math Songs, visit www.onlinemathpro.com