percent increase

Question

in 2003, the number of cell phone users was estimated at 148,000,000. by 2007, the number of cell phone users was estimated to be 168,000,000. find the percent increase

Answer 1

Let K=1000

K^2 = a million

users jumped from 148K^2 to 168K^2

percent increase is X where

168=(1+X)148 = 148 + 148X

20 = 148X

X = 20/148 = 10/74 = 5/37 = 0.135 = 13.5% increase from 2003 to 2007