Problem:
A child's wading pool contains 200 gallons of water. If water evaporates at the rate of 0.5 gallons per day and no other water is added or removed, how many gallons of water will be in the pool after 30 days?
Answer Choices:
A. 140
B. 170
C. 185
D. 198.5
E. 199.85
Solution:
​200gallons−0.5(30)gallons=200gallons−15gallons=185gallons.​
Answer: C​.
The problems on this page are the property of the MAA's American Mathematics Competitions