Question

When making a telephone call using a calling card, a call lasting 3 minutes costs $0.85. A call lasting 10 minutes costs

minutes using a calling card. Write a linear equation that models the cost of making a call lasting x minutes
Let y be the cost of making a call lasting x minutes using a calling card. Write a linear equation that models the cost of making a call lasting x mins

Answer 1

The linear equation that models the cost of making a call lasting x mins is y = 0.2834x.

SOLUTION:

Given, when making a telephone call using a calling card, a call lasting 3 minutes costs $0.85.

we need write a linear equation that models the cost of making a call lasting x minutes.

Let y be the cost of making a call lasting "x" minutes using a calling card.

Then, y = cost of making call per minute
`*` x minutes

Now, cost of making call per minute can be obtained from the case we have i.e. $0.85 per 3 minutes

Cost of call per minute =
`\frac{\text {total cost }}{\text {number of minutes}}`

Cost of call per minute =
`(0.85)/(3)`

Cost of call per minute = 0.2834

cost of call per minute is $0.2834 approximately

Now, y = 0.2834 × x

y = 0.2834x

hence, the linear equation that models the cost of making a call lasting x mins is y = 0.2834x.