Elasticity is equal to the percent change in quantity divided by the percent change in price. There is one issue with this definition; it does not specify if we are talking about the percent change going from the lower price to higher price, or higher price to lower price. Depending on which we do, we will end up with different numbers. The solution is utilizing the midpoint method. More information can be found here on the midpoint method in elasticity:

https://www.khanacademy.org/economics-finance-domain/microeconomics/elasticity-tutorial/price-elasticity-tutorial/a/price-elasticity-of-demand-and-price-elasticity-of-supply-cnx