Crutch Length Each year 15 million people have foot and ankl

Crutch Length Each year 15 million people have foot and ankle problems. Many times they need crutches. The formula f(x) = 0.72x + 2 calculates the appropriate crutch length in inches for a person with a height of x inches. (Source: Journal of the American Physical Therapy Association.) (a) Find the crutch length for a person 6 feet 3 inches tall. (b) For each 1-inch increase in height, by how much does the recommended crutch length increase?

Solution

f(x) = 0.72x + 2

a) Lenght of crutch for 6 feet 3 inches tall = 72+3 = 75 inches

Plug x= 75 in f(x) = 0.72*75 +2 = 56 inshes

b) The slope of function f(x) = 0.72 which means for 1 inch increase in height of person the crutch lenght

increases by 0.72 inch