Question

Two cell phone companies charge a flat fee plus an added cost for each minute or part of a minute used. The cost is represented by C and the number of minutes is represented by t.

Call-More: C = 0.40t + 25
Talk-Now: C = 0.15t + 40

a) Which company is cheaper if a customer talks for 50 minutes?


b) Under what conditions do the two companies charge the same?

Answer 1

a) Call-more is cheaper

b) 60 minutes

Explanation:

Call-More: C = 0.40t + 25

Talk-Now: C = 0.15t + 40

a) Substitute t = 50 minutes in the above equations.

Call-More:

C = 0.40*50 + 25

= 20 + 25

C = 45

Talk-Now:

C = 0.15*50 + 40

= 7.5 + 40

C = 47.40

Company Call-more is cheaper than Talk-now.

b) We have to find the conditions under what condition the two companies charge the same.

Charge of company Call-more = charge of company Talk-now.

0.40t + 25 = 0.15t + 40

0.40t = 0.15t + 40 -25

0.40t = 0.15t + 15

0.40t - 0.15t = 15

0.25t = 15

`\sf t = (15)/(0.25)\\\\ t = (15*100)/(25)\\\\`

t = 15*4

t = 60 minutes

Two companies charge the same for 60 minutes.