Question

Population in 1990 was 134 million. In 2000 it was 139 million. What was it in 2014

Answer 1

Well first lets find the ROC (rate of change) in the sets of data.
1990 -> 134
2000 -> 139

so lets find the difference from the years given
2000-1990=10  so there is a 10 year gab
139-134=5  so there is a 5 million increase in the population 

so divide 10 by 5 which gives us 2, so every year there is a 2 million increase in the population. so from 2000 to 2014 there is 14 years, so 
14 x 2= 28, then add that to the latest population data
139+28=167
so the population in 2014 would be 167 million 

Hope this helped!!