If the tank is already half full, that means it contains 25 litres of petrol. This means you will need to fill the remaining half, which is 25 litres.
The cost of petrol is N$13.25 per litre. To find the total cost to fill the remaining 25 litres, you can use the following calculation:
Total cost = Cost per litre × Number of litres to fill Total cost = N$13.25 × 25 litres Total cost = N$331.25
So, it will take N$331.25 to fill the tank.