Question

A pine tree measured 40 1/2 feet tall. Over the next 7 1/2 years,it grew to a height of 57 feet. During the 7 1/2 years, what was the average yearly growth rate of the height of the tree?

Answer 1

A pine tree measured 40 1/2 feet=(40 + 1/2) feet=(80+1)/2 ft=81/2 feet
it grew to a height of =57
7  1/2 years=(14+1)/2=15/2 year.

Then, during 7  1/2 years the pine tree has grown=57 ft - 81/2 ft=
=(114-81)/2 ft= 33/2 ft.


average yearly growth= (number of meters that the pine tree has grown) / number of years

average yearly growth=(33/2) ft / (15/2) years=33/15 ft / years=2.2 ft/year.

solution. 2.2 ft / year.

Answer 2

First subtract how tall it was 7 1/2 years ago from how tall it is now.57 - 40 1/2 =57 -  40.5 =  16.5 or 16 1/2So in the 7 1/2 years the tree grew 16 .5 or 16 1/2 feet. To get the average yearly growth for the 7 1/2 year period you have to divide the 16 1/2 feet by 7 1/2 years .It makes it much easier if you change the fractions to decimals. 16 1/2 = 16.57 1/2 = 7.516.5  ÷  7.5  = 2.2 or 2 1/5 feet per year! :)