Finding how long something takes when start and end times don't cross an hour boundary (e.g., 2:15 to 2:45 = 30 minutes).
Where your child meets this in real life: Working out how long a TV programme lasts or time left in a lesson
SEAGReady breaks calculate simple time durations into 3 steps, taught in order so each skill builds on the last.
Calculate how long between two times in the same hour by subtracting minutes
Given a start time and duration in minutes, find when it ends (staying within the same hour)
Given an end time and duration in minutes, find when it started (staying within the same hour)
Three free sample questions from our calculate simple time durations course. Every question comes with a full explanation, and hints that guide without giving the answer away.
Sean's swimming lesson starts at 3:10 and finishes at 3:40. How long does the lesson last?
Answer: A. 30 minutes
Both times are in the 3 o'clock hour. Subtract the minutes: 40 - 10 = 30 The lesson lasts 30 minutes.
Stuck? Start here: Both times are in the same hour (3 o'clock). What stays the same?
Niamh starts her homework at 4:10. She works for 25 minutes. What time does she finish?
Answer: B. 4:35
Start time: 4:10, duration: 25 minutes Add to minutes: 10 + 25 = 35 The hour stays at 4, so end time is 4:35.
Stuck? Start here: What is the start time and how long does she work?
Ben's favourite cartoon finishes at 5:45. The cartoon is 30 minutes long. What time did it start?
Answer: B. 5:15
End time: 5:45, duration: 30 minutes Work backwards: 45 - 30 = 15 The hour stays at 5, so start time is 5:15.
Stuck? Start here: You know when it finished and how long it was. Work backwards!
This is the exact interactive worked example your child sees in SEAGReady. Step through it and watch the method build up.
Ciara's football training starts at 4:10 and finishes at 4:45.
How long does the training last?
4:45 − 4:10
Step 1 of 3
Ciara's football training starts at 4:10 and finishes at 4:45.
How long does the training last?
Ciara's training lasts 35 minutes.
The key insight: When times are in the same hour, just subtract the minutes!
Watch out: 445 − 410 = 35. Time isn't a regular number. 4:45 doesn't equal 445 because there are 60 minutes in an hour, not 100.
These are the misconceptions we see most often in calculate simple time durations, including the ones our practice questions are specifically designed to catch.
Struggling with calculate simple time durations? The real gap is often in one of these earlier topics.
SEAGReady finds the exact step where your child gets stuck, teaches it with worked examples like the one above, and brings it back for review so it sticks.