Question

Margaret and Donovan are twins. They have each kept track of their heights every year since they were 5.

Margaret made a table to track her height in centimeters. (I wrote them as (x, y))
(5, 101); (6, 105); (7, 109); (8, 113); (9, 117); (10, 121)

Donovan wrote his height as an equation. (h = height; a = age)
h = 105 + 4.25(a - 5)

Compare their rate of changes. Who had the fastest rate of growth?

A: Donovan
B: Margaret
C: Both had the same rate of growth.
D: Not enough information to determine who had the fastest rate of growth.

Answer 1

Donovan had the fastest rate of growth among the two.

Explanation:

Rate of increment of height per year, for Margaret,

= (105 - 101)/(6 - 5)

= 4 cm / year

For Donovan, the equation describing his height (h) as a function of his age (a) is given by,

h = 105 + 4.25( a - 5)

so, rate of increment of height per year for Donovan,

= 4. 25 cm /year

So, Donovan had the fastest rate of growth among the two.