Hi! please help me solve my homework

Question

The monthly income of the workers at the Microsoft plant are distributed normally. Suppose the mean monthly income is P30,000 and the standard deviation is P5,000. 20% of workers earn how much per month?

Answer 1

use z-stat

x = earnings per month of someone in top 20% percent (80th percentile)

z = (x - mean)/SD

Find the z-score for the 80th percentile from the standard normal probability table: 0.84.

since mean = 30,000 and SD = 5,000, substituting into the above equation:

0.84 = (x - 30,000)/5000

x = 5000*0.84 + 30000 = 34,200