Telling time and elapsed time

What is this skill?

In third grade, children learn to tell time to the exact minute on an analog clock and to work out elapsed time, which is how much time passes between a start and an end. Reading 4:38 means seeing that the minute hand is three marks past the 7, counting 35, 36, 37, 38, and reading the hour hand as past the 4.

Elapsed time problems ask questions like "Soccer starts at 3:45 and lasts 40 minutes. When does it end?" or "A movie starts at 6:20 and ends at 7:05. How long is it?" Children often solve them on a number line, jumping to the next hour first: from 6:20 to 7:00 is 40 minutes, and 5 more minutes makes 45 minutes.

Why it matters

Time is part of every day, and understanding elapsed time helps children plan, wait and keep track of schedules. Knowing how much time is left before school or how long until a show starts is a useful kind of independence.

Elapsed time is also a real mathematical challenge, because time does not work in tens. An hour has 60 minutes, so 45 minutes plus 30 minutes is 1 hour 15 minutes, not 75 minutes on the clock. Working with a base of 60 strengthens number sense and problem solving, and the number line method used here is the same tool children use for adding and subtracting elsewhere.

Common mistakes

• Treating time like ordinary numbers, so 3:45 plus 30 minutes becomes 3:75. Jumping to the next hour first on a number line shows the answer is 4:15.
• Misreading the minute hand between numbers, such as reading 38 as 37 or 43. Counting by 5s to the nearest number and then by 1s helps.
• Reading the hour hand as the next hour when it is close to it. At 4:55, the hour hand is nearly on the 5, but it is still the 4 o’clock hour.
• Losing track of the hour in elapsed time problems, getting the minutes right but forgetting that the hour changed.

How to help at home

• Ask elapsed time questions about your day: "Dinner is at 6:15 and it is 5:40 now. How long until dinner?"
• Use a timer when cooking or doing chores, and ask your child to predict when it will go off.
• Draw a number line for a time problem, mark the start time, and make jumps to the next hour and then to the end time.
• Keep an analog clock visible and ask for the exact time now and then, not just the nearest five minutes.

Worked examples

These are real questions from the Tutorsaurus telling time and elapsed time practice, with the answers worked out.

1. Example 1

   What time is it?

   Choices: 1:36, 1:03, 2:06, 1:06

   Answer: 1:06. The long hand shows 6 minutes past 1. It is 1:06.

2. Example 2

   Soccer starts at 11:52 and lasts 30 minutes. What minute does it end? (type the minutes only, like 45)

   Answer: 22. 52 + 30 = 82, which is 1 hour and 22 minutes, so it ends at 12:22.

3. Example 3

   A movie starts at 2:38 and ends at 2:53. How many minutes long is it?

   Answer: 15 min. From 2:38 to 2:53 is 15 minutes.