# Math Help - Stat word problem need help URGENT

1. ## Stat word problem need help URGENT

Titan technology is a tech company that is a new cell phone service provider. Their rate for any phone call is determined as follows: the first minute costs $.15 and every minute thereafter costs$.01. Statisticians who work for Titan Technology collected information for a month regarding the costs of phone calls. The costs were normally distributed with a mean of $.25 and a standard deviation of$.03.

A. How much would a 20 minute phone call cost?

I got 34 cents but am not sure

B. Write a formula to represent the cost of a phone call. Use "c" to represent cost and "m" to represent the number of minutes.

C. A rival tech company, Idealistic Innovations, charges a flat rate of \$.29 per call. Determine when a phone call would cost the same using Idealistic and using Titan.

D. Using what you learned in part C determine the percent of calls made my Titan Technology customers that would be cheaper if they had used Idealistic Innovations instead.

2. A. That's correct

B. It's a linear formula in the form of c = am + b
a = 0.01 and b = 0.15
Therefore

c = 0.01m + 0.15

C. 0.29 = 0.01m +0.15
0.14 = 0.01m
14 = m

The phonecalls cost the same amount at 14 minutes.

D.
$

P(X > .29) = \frac{1}{\sqrt{2\pi}}\int_\infty^{.29} e^{-u^{2}/2}du

$

Which is the area under normal curve from 0.25 to $\infty$ - the area from 0.25 to 0.29

0.29 in standard units: (0.29 - 0.25) / 0.3 = $1 \frac{1}{3}$

Which yields from the standard distrbution table: 0.5 - 0.4082 = 0.0918, which gives 9.18%