# Watermelon in the sun math riddle

There is a 100 pound watermelon laying out in the sun. 89 percent of the watermelon’s weight is water. After laying out for a few hours 88 percent of the watermelon’s weight is water.

How much water evaporated?

8.33 lbs of water evaporated

(89-x) = (100-x)*.88

89-x = 88-.88x

1-x = -.88x

1=.12x

x=8.33

Where:

89-x = water loss

100-x = watermelon loss

.88 = new ratio

100-8.33=91.67 lbs (new watermelon weight)

89-8.33= 80.67 lbs (new water weight)

80.67/91.67 = 88%

1 pound of water evaporated. If the watermelon ways 100 pounds 89% would be 89 pounds.

But that would leave the watermelon at 99lbs and 88/99 isn’t 88%

11*(100/12)=91.6 gm

Almost there, but you answered the wrong question. It didn’t ask how much the watermelon weighs now, but how much water evaporated, which, by assumption, it wants that in pounds as that is the only unit of measurement given in the question.

Perhaps none of the water evaporated but instead 1% of the water was converted into the mass of the watermelon by the sun’s energy

After thinking about this a little more… The watermelon grew in size/weight potentially altering the weight in water ratio

Initial weight of non water content is 11 lbs.

Let X be the water wt. after losing water then

X/(11+X)=0.88

Solving this gives X=80.66

So lost water is 89-80.66

i.e. 8.33lbs

Simplified answer because of the way the question was worded would be 1 % of the water evaporated. This answer would suffice as it did not ask for how much the water weighed, it simply asked, ” How much water evaporated ?”.

Even in percentage terms, 1% would not be correct. Remember, percentages are relative so if dividend is not kept constant, then percentage will change. The first answer 8.33 is correct. That is equal to 9.3% of 89 lbs of water lost.

### Your Answer

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