A glass was filled with 10 ounces of water, and 0.01 ounce of the water evaporated each day during a twenty-day period. What percent of the original amount of water evaporated during this period?

2%

Explanation:

Original mass of water in glass = 10 ounces

amount that evaporates each day = 0.01 ounce

number of days = 20 days

Total amount that evaporated = 0.01 x 20 = 0.2 ounce

percentage of water that evaporated during this period = 0.2/10 x 100

                            = 2%

Hence, the percentage of the original amount of water evaporated during this period is 2%