Here is the Dublin to Cork bus timetable for this morning. Three buses make the trip, and each one stops at Portlaoise on the way. The times are written the 24-hour way, so 13:55 means just before 2 o'clock in the afternoon.

• Leaves Dublin 08:00, Portlaoise 08:50, arrives Cork 11:00
• Leaves Dublin 09:30, Portlaoise 10:25, arrives Cork 12:40
• Leaves Dublin 11:20, Portlaoise 12:10, arrives Cork 13:55

Which is the last bus you could leave Dublin on and still be in Cork before 2 o'clock in the afternoon? Have a good look before any hands go up.

The interactive shows a Dublin to Cork timetable. Watch how we read one bus down its column to find when it leaves and when it arrives, then work out how long the journey lasts. Keep an eye on which bus turns out to be the fastest.

The Earth is always turning, so different parts of the world face the sun at different moments and their clocks do not all match. Travel east and the clock is ahead of ours; travel west and it is behind. We will take one time in Dublin and work out what the clock reads in two other cities — watch which way we count.

Today we work through the timetable together: which bus and how long does it take? We'll read the row, read the column, then count on to find each journey duration before we agree the answer.

Today we find the fastest bus by working out journey durations on the interactive, then we do one time-zone stretch together on the board.

Worked example — which bus is fastest?

Read down the 08:00 column: leaves Dublin 08:00, arrives Cork 11:00. Count on from departure to arrival to find the duration.

Now the 11:20 column: leaves Dublin 11:20, arrives Cork 13:55. Count on in two steps, never subtract the minute digits. Stop at midday first, then count on to the arrival. Compare the two durations and decide which bus is faster.

Your turn on the interactive: for each challenge, tap the depart cell and the arrive cell, check the duration, and use those durations to decide which service is fastest.

Time-zone stretch on the board

A video call is set for 17:00 Dublin time. Sydney is 11 hours ahead, so count on 11 hours from 17:00. From 17:00 to midnight is 7 hours, which leaves 4 hours past midnight, so the clock in Sydney reads 04:00 the next day.

Key Takeaways

• Read across the row and down the column to find departure and arrival times.
• Count on from departure to arrival to find a journey duration; the fastest service has the shortest duration.
• Travelling east puts the clock ahead, travelling west puts it behind, so the local time shifts across time zones.

Coming Up

Next we look at converting between units of time, working out how many minutes are in a number of hours and how many hours in a number of days.