Multiplication as Repeated Addition, More Elapsed-Time Problems
Multiplication as repeated addition is introduced in Grade 4, Saxon Math Intermediate 4 Chapter 3, alongside elapsed time problems. Students learn that adding a number multiple times can be written more efficiently as multiplication: 5 added four times equals 4 times 5 equals 20. The first factor tells how many groups, and the second tells the size of each group. For example, Maria reading 30 minutes per day for 5 days is 5 times 30 equals 150 minutes total. This conceptual link bridges addition fluency to multiplication fluency.
Key Concepts
New Concept We can use multiplication to show that we want to add a number multiple times, such as adding 5 four times. $$4 \times 5 = 20$$.
What’s next Next, you’ll practice converting addition to multiplication and solve more elapsed time problems.
Common Questions
How does multiplication relate to repeated addition?
Multiplication is a shortcut for adding the same number multiple times. For example, 4 times 5 equals 20 means adding 5 four times: 5+5+5+5=20.
Which number represents how many groups in a multiplication equation?
The first factor tells how many groups. The second factor tells how many are in each group. In 4 times 5, there are 4 groups of 5.
If someone reads 30 minutes a day for 5 days, how many total minutes is that?
5 times 30 equals 150 minutes. This is equivalent to adding 30 five times: 30+30+30+30+30=150.
Can any addition problem be written as multiplication?
Only when the same number is added repeatedly. Repeated addition of equal groups can always be expressed as multiplication using the count of groups as the first factor.
What is a common mistake when converting repeated addition to multiplication?
Mixing up which number is added and which represents the count. For 4 times 5, some students write 4+4+4+4+4 instead of 5+5+5+5.