Question

suppose a 5 minute overseas call costs $5.91and a 10 minute call costs $10.86. The cost of the call and the length of the call are related. The cost of each minute is constant.​

Answer 1

C=0.96 + 0.99 t

Explanation:

Let the cost of the call (C) and the time of call (t) are related by the relation

C = a + bt ......(1)

Hence, the fixed cost for every call is a and the cost of the call per minute b is added to this.

Now, given that, 5 minutes call costs $5.91 and the 10 minutes call costs $10.86.

Therefore, from equation (1), we get

5.91 = a + 5b ....... (2) and

10.86 = a + 10b ....... (3)

Now, solving equation (2) and (3) we get, 5b = 4.95 , ⇒ b =0.99

Hence, from equation (2), we get, a = 5.91 - 5×0.99 = 0.96.

Therefore, the relation between time of the call and the cost of call is given by C=0.96 + 0.99 t (Answer)