A 50-lb watermelon is 99%. What does it weigh after some

[lwarner]

There is a watermelon it is 99% water and it weighs 50 lbs, after being in the sun some of it evaporates it is now 98% water, what does it weigh?

How do I start this problem? It is ratios?

 

[tkhunny]

A very creative variation to the standard mixture problem.

Just find something to equate. You can use "Water" or "Not Water". Either way.

Water:

x is the new weight
(50-x) is the weight of the water evaporated

50 lbs*99%water - (50-x) lbs*100%water = x lbs*98%water

50*0.99 - (50-x) = x*0.98

50*0.99 - 50 + x = x*0.98

-50*0.01 = x*0.98 - x

-50*0.01 = -x*0.02

x = 50*0.01/0.02 = 25

25 pounds!! Wow. I didn't expect that.

Let's do it by equating NONwater and see if the result is the same.

99% water ==> 1% NONwater

50 lbs * 1%NONwater - (50-x) lbs*0%NONwater = x lbs * 2%NONwater

50*0.01 = x*0.02

x = 50*0.01/0.02 = 25

That was even easier!!

Note: Generally, the one with the zero (0) percent is the easier of the two.