Answer:
a) 20.16; b) 20.49 and 21.51
Step-by-step explanation:
We use z scores for each of these. The formula for a z score is
.
For part a, we want the 20th percentile; this means we want 20% of the data to be lower than this. We find the value in the cells of the z table that are the closest to 0.20 as we can get; this is 0.2005, which corresponds with a z score of -0.84.
Using this, 21 as the mean and 1 as the standard deviation,
-0.84 = (X-21)/1
-0.84 = X-21
Add 21 to each side:
-0.84+21 = X-21+21
20.16 = X
For part b, we want the middle 39%. This means we want 39/2 = 19.5% above the mean and 19.5% below the mean; this means we want
50-19.5 = 30.5% = 0.305 and
50+19.5 = 69.5% = 0.695.
Looking these values up in the cells of the z table, we find those exact values; 0.305 corresponds with z = -0.51 and 0.695 corresponds with z = 0.51:
-0.51 = (X-21)/1
-0.51 = X-21
Add 21 to each side:
-0.51+21 = X-21+21
20.49 = X
0.51 = (X-21)/1
0.51 = X-21
Add 21 to each side:
0.51+21 = X-21+21
21.51 = X
Answer:
6
Step-by-step explanation:
Answer:
(2)/(3) =( 4)/( 3+x)
Cross multiply
2*(3+x)= 4*3
Solve bracket
6+2x=12
Subtract 6 from both sides
2x=6
Divide both sides by 2
x=3
Hope it helps :-)
Let's assume two variables x and y which represent the local and international calls respectively.
x + y = 852 = total number of minutes which were consumed by the company (equation 1)
0.06*x+ 0.15 y =69.84 = total price which was charged for the phone calls (Equation 2)
from equation 1:-
x=852 -y (sub in equation 2)
0.06 (852 - y) + 0.15 y =69.84
51.12 -0.06 y +0.15 y =69.84 (subtracting both sides by 51.12)
0.09 y =18.74
y= 208 minutes = international minutes (sub in 1)
208+x=852 (By subtracting both sides by 208)
x = 852-208 = 644 minutes = local minutes