Two trips are on the table for our class: Glendalough, with its lakes and old round tower in Wicklow, or Newgrange, the ancient tomb in Meath.

We have a budget of €175 for each pupil, a school day from 09:00 to 14:40, and 28 pupils going.

One of these trips fits our day and our budget more easily than the other. Which one do you think it is? And what do we need to work out before we can be sure?

Here are the two trips side by side. Look at how each cost and each time lines up against the other.

Now the same two trips as costs. These cards show that the bus is one price for the whole class, but entry and lunch are a price for each pupil.

Before the next card lands, predict which trip costs each pupil more, and by how much.

Today we work through two things together on the board: what each pupil pays, and how long the day is.

We will put the two trips into a budget chart so we can see each cost on its own row. For Glendalough we enter the bus share €10, entry €7 and lunch €5. For Newgrange we enter the bus share €12.50, entry €9 and lunch €5. The chart shows each cost as its own row, the running total, and how much of the €175 is left over for extras.

Once both totals are up, we will look back at the times: Glendalough spends 2 h 30 m of the day travelling, Newgrange only 1 h 40 m. So which limit really decides between them, the money or the day?

Today we plan one trip's cost for each pupil, adding it up bit by bit and staying under €175. We enter each amount at the board and check the running total.

We build four plans in turn:

• Glendalough: bus €10, entry €7, lunch €5
• the same Glendalough plan plus a €3 souvenir
• Newgrange: bus €12.50, entry €9, lunch €5
• Newgrange plus a €10 guided tour

After the tool confirms each total, we say aloud whether it still comes in under €175.