A movie starts at 2:10 and ends at 2:40. A student says 'the elapsed time is 2:40.' What mistake did this student make?
AThe student is correct — elapsed time is always the end time
BThe student confused elapsed time with the end time; the elapsed time is 30 minutes
CThe student should have counted backward from 2:40 to find the answer
DThe student needed to subtract 2:10 from 12:00 first
Elapsed time is the distance between start and end — how much time passed — not the clock reading at the end. To find it, count forward from 2:10: 2:15, 2:20, 2:25, 2:30, 2:35, 2:40 — six jumps of 5 minutes = 30 minutes. The end time (2:40) and the elapsed time (30 minutes) are two completely different things.
Question 2 Multiple Choice
Class starts at 1:15 and ends at 1:45. A student counts forward: 1:20, 1:25, 1:30, 1:35, 1:40, 1:45 — six jumps of 5 minutes. What is the elapsed time?
A45 minutes — read the minute hand at the end time
B15 minutes — read the minute hand at the start time
C30 minutes — six jumps of 5 minutes each
D60 minutes — count from the top of the hour to the end
The counting strategy is: start at the beginning time and count forward in 5-minute hops until you reach the end time, keeping track of how many hops you took. Six hops × 5 minutes = 30 minutes elapsed. The end-time minute hand reading (45) is not the elapsed time — it's just where the clock points when class finishes.
Question 3 True / False
Elapsed time tells you how much time has passed between start and end — it is not the same as the clock reading when you finish.
TTrue
FFalse
Answer: True
This is the central distinction. End time is a clock position; elapsed time is a duration — a measurement of how much time went by. A movie ending at 3:00 has an end time of 3:00, but its elapsed time might be 90 minutes, 45 minutes, or any other length depending on when it started.
Question 4 True / False
To find elapsed time, you should count backward from the end time to the start time.
TTrue
FFalse
Answer: False
Always count forward from start to end. Time moves forward, and the counting strategy mirrors that direction: begin at the start time and hop forward in 5-minute intervals until you reach the end time. Counting backward is the most common error at this level — it can produce wrong answers and causes confusion about the direction of time.
Question 5 Short Answer
A class starts at 3:20 and ends at 3:50. Explain how you would use counting forward to find the elapsed time.
Think about your answer, then reveal below.
Model answer: Start at 3:20 and count forward in 5-minute jumps: 3:25, 3:30, 3:35, 3:40, 3:45, 3:50. That is six jumps. Six jumps × 5 minutes each = 30 minutes of elapsed time.
The counting strategy makes elapsed time concrete and reduces the chance of reading the end time as the answer. Drawing a timeline with tick marks for each 5-minute interval is especially helpful for students who lose count — it makes the hops visible.