Telephone charges

Question

Todd's telephone company charges $ 0.04 per minute for weekend calls and $ 0.07

per minute for calls made on weekdays. This month Nick was billed for 571

minutes. The charge for these minutes was $ 27.76 .
  
How many minutes did he talk on weekends and how many minutes did he talk on? weekdays?

Answer 1

N1 = Number of minutes spent calling during the week. N2 = Number of minutes spent spent calling during the weekend. Total number of minutes billed was 571. So we have N1 + N2 = 571 ==> N1 = 571 - N2. We're going to use this for substitution to solve the problem.

 

Now the total bill was 27.76. This means that 0.04*N1 + 0.07*N2 = 27.76. Now we apply substitution to get 0.04*(571 - N2) + 0.07N2 = 27.76 ==> 22.84 + 0.07N2 - 0.04N2 = 27.76 ==> 0.03N2 = 4.92 ==> N2 = 164.

 

So now we know the number of minutes spent calling on the weekend was 164. N1 = 571 - 164 = 407. So the number of minutes spent calling during the week was 407.