10s multiplication facts
The 10s multiplication facts in Grade 4 are the simplest in the times table: to multiply any whole number by 10, simply attach a zero to the end of the number. So 7 x 10 = 70, and 12 x 10 = 120. Covered in Saxon Math Intermediate 4, Chapter 4, mastering 10s multiplication builds understanding of our base-ten number system (each place value is ten times the one to its right) and directly supports mental math, estimation, and multiplication by multiples of 10 in later grades.
Key Concepts
Property To find the product of a whole number and 10, we simply attach a zero to the end of the whole number.
Example 1. $8 \times 10$: Attach a zero to 8 to get 80. So, $8 \times 10 = 80$. 2. $12 \times 10$: Attach a zero to 12 to get 120. So, $12 \times 10 = 120$.
Explanation Multiplying by 10 is the easiest trick in the book. Just take the number you are multiplying and add a zero to the end of it. This works because our number system is based on groups of ten, so multiplying by 10 moves every digit one place over to the left.
Common Questions
What is the rule for multiplying by 10?
To multiply any whole number by 10, attach one zero to the right end of the number. For example, 8 x 10 = 80, and 25 x 10 = 250.
Why does multiplying by 10 add a zero?
Our base-ten number system means each position is worth ten times the one to its right. Multiplying by 10 moves every digit one place to the left, and a zero fills the now-empty ones place.
What happens when you multiply by 100 or 1000?
Multiplying by 100 adds two zeros, and multiplying by 1000 adds three zeros. This is because 100 = 10 x 10 and 1000 = 10 x 10 x 10. Each factor of 10 adds one more zero.
When do students learn the 10s multiplication facts?
Students learn 10s multiplication in Grade 3 and reinforce fluency in Grade 4. Saxon Math Intermediate 4 covers 10s facts in Chapter 4, Lessons 31-40.
How do 10s facts connect to multiplying by multiples of 10?
To multiply 7 x 30, think: 7 x 3 = 21, then attach one zero for the tens: 210. Knowing that 7 x 10 = 70 extends to 7 x 20 = 140, 7 x 30 = 210, and so on.
How do 10s multiplication facts help with mental math?
Multiplying by 10 is the backbone of mental multiplication. Quick estimation often involves rounding to the nearest 10 and multiplying. Knowing 7 x 10 = 70 instantly gives a quick estimate for 7 x 9 (about 63) or 7 x 11 (about 77).
Do decimals change when you multiply by 10?
Yes. Multiplying a decimal by 10 moves the decimal point one place to the right. For 2.5 x 10 = 25.0. This is because multiplying by 10 shifts every digit one place to the left relative to the decimal point.