In the last lesson, you learned how to multiply numbers by 10.
To multiply a number by 10, just add '0' to its end!
10 × 2 = 20
10 × 5 = 50
10 × 99 = 990
Numbers that end with a 0 are called multiples of 10.
Let's try multiplying 7 by a multiple of 10, 40.
7 × 40 = ?
Let's split the multiple of 10 into 10 and another factor.
7 × 40 = 7 × 4 × 10
Now, we can multiply 7 and 4 together, which you should have memorized by now.
7 × 4 × 10 = 28 × 10
Finally, we just add a '0' after the 28.
28 × 10 = 280
So,
7 × 40 = 280
Well done! 👏
Let's try another example.
9 × 20 = ?
First, multiply the non-zero digits, then add the 0 digit.
9 × 20 = 18 × 10 = 180
Nice job! 👍
Do you see a pattern in these answers?
To multiply a number by a multiple of 10, multiply the non-zero digits first, then add back the 0's.
Let's try some more examples:
6 × 30 = 180
50 × 8 = 400
110 × 5 = 550
3 × 120 = 360
Great job.
Now, let's complete the practice to help you master the skill.