Answer
(a) 1.5-2.5 feet tall
(b) 8400 months
(c) 840 years
Work Step by Step
(a)
We convert the minimum and maximum heights of the trees to feet:
$18~inches*\frac{1~foot}{12~inches}=1.5~feet=1\frac{1}{2}~feet$
$30~inches*\frac{1~foot}{12~inches}=2.5~feet=2\frac{1}{2}~feet$
Thus the trees are 1.5-2.5 feet tall.
(b)
We convert years to months:
$700~years*\frac{12~months}{1~year}=8400~months$
(c)
First, we convert 3 feet to inches in order to use the same units for the comparison:
$3~feet*\frac{12~inches}{1~foot}=36~inches$
Next, we set up a proportion to find out how long it would take the tree to reach a height of $36~inches$:
$\displaystyle \frac{x}{36~inches}=\frac{700~years}{30~inches}$
We cross-multiply:
$30x=700*36$
$30x=25200$
$x=25200/30$
$x=840~years$
Thus it would take 840 years (140 years more).
