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Lesson 3: Elapsed time

# Time FAQ

## What do the different hands on a clock mean?

On a clock there are two hands. The start color #bc2612, start text, h, o, u, r, space, h, a, n, d, end text, end color #bc2612 is the shorter hand. The start color #0c7f99, start text, m, i, n, u, t, e, space, h, a, n, d, end text, end color #0c7f99 is the longer hand.

## How do I read a clock?

First, we need to look at the hour hand. The hour hand is between 1 and 2, so it is after 1 o'clock but not yet 2 o'clock.
So, the hour is 1. Next, we look at the minute hand.
The minute hand starts pointing straight up for 0 minutes.
When counting minutes, the distance between each tick mark represents 1 minute.
Each number on the clock represents 5 minutes, with a total of start color #0c7f99, 60, end color #0c7f99 minutes in each hour.

## How can a number line help us find elapsed time?

If we unroll a clock, it becomes a number line! We can set up a number line to represent minutes in an hour. Then, we can mark the start time and end time of an event, and count the number of minutes between the two marks.
To find out how many minutes are between start color #208170, 9, colon, 18, end color #208170 to start color #bc2612, 9, colon, 57, end color #bc2612, we can find the distance from start color #208170, 9, colon, 18, end color #208170 to start color #bc2612, 9, colon, 57, end color #bc2612.
\begin{aligned} \tealE{9{:}18} +{} &\purpleD{2}\text{ minutes} = 9{:}20\\\\ 9{:}20 +{} & \goldE{30}\text{ minutes} = 9{:}50 \\\\ 9{:}50 +{}&\blueE{7}\text{ minutes} = \redE{9{:}57} \end{aligned}

## Why do we need to know how to calculate elapsed time?

Knowing how to calculate elapsed time helps us understand how long it takes to do certain things, like driving to a new place or completing a task.

## How can we use what we learned in this unit in the real world?

Time is an important part of our lives, so this unit has many real-world applications. We can use what we learned to keep appointments, plan our day, and understand how long things take.