Bunuel wrote:

A nursery stocks only pine trees and maple trees. If the average height of a pine tree is 18 feet and the average height of a maple tree is 14 feet and 60% of the trees in the nursery are maple trees, what is the average height, in feet, for all trees at the nursery?

A. 15.2

B. 15.6

C. 16

D. 16.4

E. 16.8

You can calculate the average height directly (because percents sum to 1). If 60% are maple, M, then 40% are pine, P

Average height =

(% of M)*(Height of M) + (% of P)*(Height of P)

Average height,

\(A= (.6*14) + (.4*18)\)

\(A = 7.2 + 8.4\)

\(A = 15.6\) ANSWER B

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