Question

A certain variety of pine tree has a mean trunk diameter of y = 150 cm and a
standard deviation of o = 30 cm.
A certain section of a forest has 500 of these trees.
Approximately how many of these trees have a diameter smaller than 120 cm?

Answer 1

Answer:

80 trees have a diameter smaller than 120cm

Step-by-step explanation:

Step 1

To solve this question, we would make use of the Z score formula.

z = x - μ/σ

Where

z = z score

x = Raw score = 120cm

μ = Population mean = 150cm

σ = Population standard deviation = 30cm

Hence,

z =120 - 150/30

z = -1

The z score = -1

Step 2

We find the Probability of the calculated z score using the z score table.

P(z) = P(z = -1) = P(x<120) = 0.15866

Approximately to the nearest hundredth = 0.16

Converting to percentage = 0.16 × 100 = 16%

The percentage of trees with a diameter smaller than 120cm = 16%

Therefore, the number of trees with a diameter smaller than 120cm

= 16% × 500 trees = 80trees