Grade 2
  1. Number Sense and Operations  1.1. Counting and Number Sequences  1.1.1. Counting up to 100  1.1.2. Counting by 2s, 5s, and 10s  1.1.3. Counting Backward from 20  1.1.4. Odd and even numbers in counting sequences  1.2. Place Value  1.2.1. Understanding ones and tens  1.2.2. Comparing Two-Digit Numbers  1.2.3. Identifying the Value of Each Digit in a Number  1.2.4. Building numbers using tens and ones  1.3. Addition and Subtraction  1.3.1. Basic addition up to 20  1.3.2. Basic subtraction up to 20  1.3.3. Addition with Regrouping  1.3.4. Subtraction with Borrowing  1.3.5. Solving word problems involving addition and subtraction  1.3.6. Addition and Subtraction with Multiples of 10  1.4. Odd and Even Numbers  1.4.1. Identifying Odd and Even Numbers  1.4.2. Understanding patterns in odd and even numbers  1.4.3. Simple operations with odd and even numbers
  2. Fractions and Decimals  2.1. Introduction to Fractions  2.1.1. Understanding halves and quarters  2.1.2. Representing fractions visually  2.1.3. Simple Fraction Comparisons  2.1.4. Writing Simple Fractions  2.1.5. Fractions as part of a whole  2.2. Fraction Equivalency  2.2.1. Understanding Equal Parts  2.2.2. Identifying Equivalent Fractions
  3. Measurement and Data  3.1. Length Measurement  3.1.1. Measuring objects using rulers  3.1.2. Comparing lengths  3.1.3. Estimating lengths  3.1.4. Understanding units of measurement (centimeters and inches)  3.1.5. Relating Length Measurements to Real-World Objects  3.2. Weight and Mass Measurement  3.2.1. Comparing Weights of Objects  3.2.2. Estimating weight in grams and kilograms  3.2.3. Using balance scales for comparison  3.3. Volume and Capacity Measurement  3.3.1. Understanding capacity with cups and liters  3.3.2. Comparing capacities of containers  3.3.3. Introduction to Milliliters  3.4. Time  3.4.1. Reading analog and digital clocks  3.4.2. Understanding hours and minutes  3.4.3. Calculating elapsed time in hours  3.4.4. Days of the week and months of the year  3.4.5. Understanding AM and PM  3.5. Money  3.5.1. Recognizing coins and bills  3.5.2. Counting money up to $1  3.5.3. Simple Addition and Subtraction with Money  3.5.4. Making Change for a Dollar
  4. Geometry and Spatial Reasoning  4.1. Shapes and Their Attributes  4.1.1. Identifying basic shapes (circle, triangle, square, rectangle)  4.1.2. Understanding sides and corners  4.1.3. Distinguishing between 2D and 3D shapes  4.1.4. Recognizing 3D Shapes (Cube, Sphere, Cone, Cylinder)  4.1.5. Composing and Decomposing Shapes  4.2. Symmetry  4.2.1. Understanding Lines of Symmetry  4.2.2. Drawing Symmetrical Shapes  4.2.3. Identifying Symmetrical Objects in the Environment  4.3. Patterns and Spatial Awareness  4.3.1. Recognizing and Creating Patterns  4.3.2. Extending Patterns  4.3.3. Understanding positions (left, right, above, below)  4.3.4. Using a grid to locate objects
  5. Data Handling and Probability  5.1. Collecting and Organizing Data  5.1.1. Using tally marks  5.1.2. Reading Bar Graphs  5.1.3. Simple Pictographs  5.1.4. Creating Bar Graphs from Given Data  5.2. Interpreting Data  5.2.1. Answering questions based on data  5.2.3. Identifying Most and Least in Data Sets  5.3. Introduction to Probability  5.3.1. Understanding likely and unlikely events

Grade 2 → Measurement and Data → Time ↓


Calculating elapsed time in hours


Time is an integral part of our daily lives, and it is important to understand how to measure and interpret it. One of the fundamental aspects of dealing with time is calculating elapsed time. In this lesson, we will explore how to count elapsed time in hours, focusing on understandable methods for grade 2 math.

Understanding time

Before we start calculating the elapsed time, let's ensure a basic understanding of time. In our daily lives, time is measured in units such as seconds, minutes, and hours. A 24-hour day is divided into smaller segments:

  • 1 hour = 60 minutes
  • 1 minute = 60 seconds

For Grade 2, we will focus on hours and minutes, which are most commonly used in their everyday experiences. Let's start with an example.

What is the elapsed time?

Elapsed time is the time that passes from the start of an event to its end. For example, if you start watching a movie at 4:00 PM and it ends at 6:00 PM, the elapsed time is the period between 4:00 PM and 6:00 PM.

See the time on the clock

The easiest way to measure elapsed time is to use a clock. Let's look at an example:

12 3 6 9

Consider the clock above. Suppose the short needle (hour hand) points to 3 and the long needle (minute hand) points to 12. This indicates that the time is 3 PM. If your program starts at 3:00, we can use this visualization to understand when it ends by moving the hour hand.

Simple elapsed time example

Let us calculate the elapsed time if a task starts at 2 PM and ends at 5 PM.

Kickoff: 2pm End: 5pm

From a start time of 2 PM, the clock's hour hand will point to 2. At an end time of 5 PM, it will point to 5. To find the elapsed time, count the number of steps per hour taken by the hour hand to go from 2 to 5. Here, it is:

5 - 2 = 3 hours

This means that 3 hours have passed.

Time in half hours and hours

Let's consider a situation where we deal with half an hour. What if an event starts at 3:30 PM and ends at 5:00 PM?

Kickoff: 3:30 PM End: 5pm

The starting time, 3:30 PM, means that the minute hand is at 6 on the clock face, indicating the 30th minute of the hour. The ending time is straightforward. The steps involve counting the hours from 3:30 PM to 5:00 PM. Since the time from 3:30 PM to 4:00 PM is half an hour and the time from 4:00 PM to 5:00 PM is one hour, the elapsed time is:

0.5 + 1 = 1.5 hours

Understanding AM and PM

It's important to note that time is usually divided into two parts: AM and PM. AM stands for ante meridiem, which means before noon, and PM stands for post meridiem, which means after noon. Be sure to differentiate between these when calculating elapsed time, as this can significantly change the result.

A comprehensive example

Let's look at a scenario with time intervals of morning and afternoon. Imagine you start a picnic at 10:00 am and end it at 3:00 pm. To find the total time spent on the picnic:

Start: 10am End: 3 PM

Calculate the hours from 10 AM to 3 PM:

3 - 10 = 5 hours

The elapsed time is 5 hours.

Practice exercises

Exercise 1

If your school starts at 8 a.m. and ends at 2 p.m., how many hours are you in school?

6 hours

Exercise 2

A football match starts at 4:00 pm and ends at 7:00 pm. Calculate the duration of the football game.

3 hours

Exercise 3

Your family travels from 9:30 a.m. to 1:00 p.m. How long was the trip?

3.5 hours

Conclusion

Counting elapsed time in hours is a basic skill that helps us manage our daily schedule. It helps children understand the concept of time and its measurement, which they can apply in real-world situations. By practicing various examples and using visual representations such as clocks, learners can understand these concepts effectively, laying the groundwork for more advanced time-related calculations in the future.


Grade 2 → 3.4.3


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Understanding hours and minutes
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Days of the week and months of the year

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Calculating elapsed time in hours

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