A service costs R2.50 per minute. Calculate the total cost for 0, 5, 10, 15, 20, and 30 minutes. Describe the relationship between minutes and cost.

The cost per minute is R2.50. The total cost (C) is calculated by multiplying the minutes (m) by R2.50.

For $m=0$: $C = 2.50 \times 0 = 0$
For $m=5$: $C = 2.50 \times 5 = 12.50$
For $m=10$: $C = 2.50 \times 10 = 25.00$
For $m=15$: $C = 2.50 \times 15 = 37.50$
For $m=20$: $C = 2.50 \times 20 = 50.00$
For $m=30$: $C = 2.50 \times 30 = 75.00$

The completed table is:

As the minutes increase, the total cost increases proportionally. For every additional minute, the cost increases by a constant amount.

The cost per additional minute is given in the problem statement.
The cost per additional minute is R2.50.

The relationship is increasing. This is because for every additional minute, the total cost increases by a positive amount (R2.50), meaning the total cost always goes up as the number of minutes increases.

Let C be the total cost and m be the number of minutes.
The formula for total cost (C) in terms of minutes (m) is:

To calculate the cost for 12 minutes, substitute $m=12$ into the formula:

The cost for 12 minutes is R30.00.

From the table, the cost for 10 minutes is R25.00 and for 15 minutes is R37.50.
The cost for 12 minutes (R30.00) fits the pattern because it is greater than the cost for 10 minutes and less than the cost for 15 minutes.
Specifically, 12 minutes is 2 minutes more than 10 minutes.
Increase in cost = $2 \text{ minutes} \times \text{R}2.50/\text{minute} = \text{R}5.00$.
Cost for 12 minutes = Cost for 10 minutes + R5.00 = R25.00 + R5.00 = R30.00.
This confirms the answer fits the pattern of R2.50 per minute.