Conisder that the cases of measles in 2014 and 2015 were, respectively:
2014: 300,000 (approximately)
2015: 250,000
In order to determine the percentage of decrease, proceed as follow:
subtract 250,000 to 300,000:
300,000 - 250,000 = 50,000
next, calculate the relative percentage of 50,000 related to 300,000. If x is such percentage, then, you can write:
By solving for x, you obtain:
Hence, by approximately 16.7% the measles declined between 2014-2015