Problem
Compare hours first, then minutes
The clocks show when Liam, Mia, and Noah arrived at school this morning. Liam arrived at 8:43, Mia at 9:00, and Noah at 8:28. Which student arrived at school first?
Measurement & data
Your answer
Watch out Don't compare just the minutes — Mia's :00 looks smallest, but she's in the 9 o'clock hour, so she's later than Liam and Noah, who are both in the 8 o'clock hour. Compare the hour first.
How to solve
Strategy Draw a Diagram — Read each clock to get the time, then compare the hour first and only compare the minutes when the hours tie, to find the earliest time.
1STEP 1
Read each clock
Liam arrived at 8:43, Mia at 9:00, and Noah at 8:28.
Liam 8:43, Mia 9:00, Noah 8:28
The short hand shows the hour and the long hand shows the minutes. Reading both hands' positions tells us the exact time each student arrived.
Draw A Diagram2.MD.C.7Time2STEP 2
Compare the hours
Liam and Noah are in the 8 o'clock hour, so Mia (9:00) isn't first.
8 is less than 9
The hour is the bigger unit of time and the minute is the smaller unit inside it. The 8 o'clock hour holds exactly 60 minutes before it turns to 9:00, so any time in the 8 o'clock hour is always earlier than 9:00, no matter the minutes.
Systematic List2.MD.C.7TimeBecause 8 o'clock is earlier than 9 o'clock, Mia at 9:00 cannot be the earliest arrival, so the first student is Liam or Noah.
Why?
A student in the 8 o'clock hour arrived before a student in the 9 o'clock hour, no matter how many minutes each clock shows.
Why?
The hour names the bigger part of the time and the minutes name the smaller part, so a difference in the hour settles who is earlier before the minutes are even looked at.
Why?
The 8 o'clock hour holds exactly 60 minutes, so once those minutes are used up the clock turns to 9:00 and every 8-something time has already gone by.
🧱A bigger unit is a fixed count of smaller unitsA bigger unit always equals the same fixed number of smaller units (1 hour = 60 minutes, 1 km = 1000 m), so a measure can be renamed between them.
3STEP 3
Compare the minutes within the 8 o'clock hour
Liam is 43 minutes, Noah is 28 — since 28 is less than 43, Noah arrived first.
28 is less than 43
When the hour is the same, a smaller minute count means less time has passed since that hour began, so it's earlier. 28 is less than 43, so Noah arrived before Liam.
Systematic List2.MD.C.7TimeAnswer
Noah
8:28 → 8:43 → 9:00 (earliest to latest)
Check — ordering the three times from earliest: 8:28 (Noah), 8:43 (Liam), 9:00 (Mia), so Noah is first.
Takeaway
When comparing clock times, compare the hour first, and only compare minutes when the hours are the same.
- Read the times → Liam 8:43, Mia 9:00, Noah 8:28
- Compare hours → the 8 o'clock hour (Liam, Noah) beats 9:00 (Mia)
- Compare minutes → 28 is less than 43, so Noah is first
Where next?
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