In this Grade 4 Saxon Math Intermediate 4 lesson, students learn to recognize multiplication as repeated addition, converting expressions like 6 + 6 + 6 + 6 + 6 into multiplication problems using the multiplication sign and notation. The lesson also extends students' understanding of elapsed time, practicing how to count forward and backward on a clock to solve problems involving hours and minutes. Both concepts are reinforced through hands-on practice with student clocks and written exercises integrating earlier skills.
Section 1
📘 Multiplication as Repeated Addition, More Elapsed-Time Problems
We can use multiplication to show that we want to add a number multiple times, such as adding 5 four times.
Next, you’ll practice converting addition to multiplication and solve more elapsed-time problems.
Section 2
Multiplication as Repeated Addition
Multiplication is a method for representing repeated addition. An addition problem like can be written as the multiplication problem .
Instead of writing out a long, tedious chain of the same number being added over and over, like a never-ending conga line, multiplication is your awesome shortcut. It lets you quickly say, "I have this many groups of that specific number." It is a super-fast way to count things that come in identical sets, like packs of gum or legs on spiders!
Section 3
Elapsed Time
Elapsed time is the amount of time that passes between two different points in time. To find a future time, you can count forward from a starting time.
Find the time 2 hours and 40 minutes after 3:30 p.m. -> Step 1: 3:30 p.m. + 2 hours = 5:30 p.m. Step 2: 5:30 p.m. + 40 minutes = 6:10 p.m.
Find the time 1 hour and 50 minutes after 8:20 a.m. -> Method 2: 8:20 a.m. + 2 hours = 10:20 a.m., then 10:20 a.m. - 10 minutes = 10:10 a.m.
Ever wonder what time your video game marathon will finally end? That is an elapsed time problem you can solve by “time-traveling” forward on a clock. A clever trick is to jump ahead by the full hours first, since that is easy, and then simply add the leftover minutes. You can even overshoot your target time and just hop backward a little!
Section 4
Finding a Past Time
To find a time that occurred in the past, you must count backward from a known, later time.
What time was it 3 hours and 10 minutes before 1:30 p.m.? -> Step 1: 1:30 p.m. - 3 hours = 10:30 a.m. Step 2: 10:30 a.m. - 10 minutes = 10:20 a.m.
When did the movie start if it ended at 9:05 p.m. and was 2 hours 15 minutes long? -> Step 1: 9:05 p.m. - 2 hours = 7:05 p.m. Step 2: 7:05 p.m. - 15 minutes = 6:50 p.m.
Imagine you know a big event happened today, but you need to figure out when it actually started. This is like being a time detective and rewinding the clock! You start at the end time and travel backward. Just like with going forward, it is easiest to take big leaps backward with the hours first, and then carefully step back by the minutes.
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Section 1
📘 Multiplication as Repeated Addition, More Elapsed-Time Problems
We can use multiplication to show that we want to add a number multiple times, such as adding 5 four times.
Next, you’ll practice converting addition to multiplication and solve more elapsed-time problems.
Section 2
Multiplication as Repeated Addition
Multiplication is a method for representing repeated addition. An addition problem like can be written as the multiplication problem .
Instead of writing out a long, tedious chain of the same number being added over and over, like a never-ending conga line, multiplication is your awesome shortcut. It lets you quickly say, "I have this many groups of that specific number." It is a super-fast way to count things that come in identical sets, like packs of gum or legs on spiders!
Section 3
Elapsed Time
Elapsed time is the amount of time that passes between two different points in time. To find a future time, you can count forward from a starting time.
Find the time 2 hours and 40 minutes after 3:30 p.m. -> Step 1: 3:30 p.m. + 2 hours = 5:30 p.m. Step 2: 5:30 p.m. + 40 minutes = 6:10 p.m.
Find the time 1 hour and 50 minutes after 8:20 a.m. -> Method 2: 8:20 a.m. + 2 hours = 10:20 a.m., then 10:20 a.m. - 10 minutes = 10:10 a.m.
Ever wonder what time your video game marathon will finally end? That is an elapsed time problem you can solve by “time-traveling” forward on a clock. A clever trick is to jump ahead by the full hours first, since that is easy, and then simply add the leftover minutes. You can even overshoot your target time and just hop backward a little!
Section 4
Finding a Past Time
To find a time that occurred in the past, you must count backward from a known, later time.
What time was it 3 hours and 10 minutes before 1:30 p.m.? -> Step 1: 1:30 p.m. - 3 hours = 10:30 a.m. Step 2: 10:30 a.m. - 10 minutes = 10:20 a.m.
When did the movie start if it ended at 9:05 p.m. and was 2 hours 15 minutes long? -> Step 1: 9:05 p.m. - 2 hours = 7:05 p.m. Step 2: 7:05 p.m. - 15 minutes = 6:50 p.m.
Imagine you know a big event happened today, but you need to figure out when it actually started. This is like being a time detective and rewinding the clock! You start at the end time and travel backward. Just like with going forward, it is easiest to take big leaps backward with the hours first, and then carefully step back by the minutes.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter