This video shows how to back out changes in quantity demanded from information on price elasticity of demand and changes in price. The problem is taken from Principles of Microeconomics, 6th Edition, by N. Gregory Mankiw, and is Ch. 5 problem #3. See the "Practice Problems" playlist for an archive of daily practice problems. For more information and a complete listing of videos and online articles by topic or textbook chapter, see http://www.economistsdoitwithmodels.com/economics-classroom/ For t-shirts and other EDIWM items, see http://www.economistsdoitwithmodels.com/merch/ By Jodi Beggs - Economists Do It With Models http://www.economistsdoitwithmodels.com/ Facebook: http://www.facebook.com/economistsdoitwithmodels Twitter: http://www.twitter.com/jodiecongirl Tumblr: http://economistsdoitwithmodels.tumblr.com/