Multiplying by Tens, Hundreds and Thousands
Learn to multiply by tens, hundreds and thousands such as 20, 60, 400 and 4,000: multiply by one digit first, then by 10, 100 or 1,000.
1. Multiplying by Tens (20, 30, 60...)
The Strategy
To multiply by 20, 30, 40, etc., break it into two steps:
- Multiply by the digit (2, 3, 4, etc.)
- Then multiply by 10
Example: Multiply 43 by 20
20 is the same as 2 × 10
43 × 20 = 43 × 2 × 10
= 86 × 10
= 860
More Examples:
134 × 60 = 134 × 6 × 10 = 804 × 10 = 8,040
56 × 50 = 56 × 5 × 10 = 280 × 10 = 2,800
2. Multiplying by Hundreds and Thousands (400, 600, 4,000...)
The Strategy
Same idea! To multiply by 400, 600, 4,000, etc., break it into two steps:
- Multiply by the digit (4, 6, etc.)
- Then multiply by 100 (for thousands, by 1,000)
Example: Multiply 68 by 400
400 is the same as 4 × 100
68 × 400 = 68 × 4 × 100
= 272 × 100
= 27,200
Example: Multiply 314 by 600
314 × 600 = 314 × 6 × 100
= 1,884 × 100
= 188,400
Example: Multiply 23 by 4,000
4,000 is the same as 4 × 1,000
23 × 4,000 = 23 × 4 × 1,000
= 92 × 1,000
= 92,000
3. Alternative Methods
Can you think of another way?
To find 134 × 60, you can multiply by 6 first or by 10 first:
134 × 60 = 134 × 6 × 10 = 804 × 10 = 8,040
Or: 134 × 60 = 134 × 10 × 6 = 1,340 × 6 = 8,040
Both ways give the same answer!
Practice Problems
1. Multiply:
a) 26 × 30 = ?
b) 407 × 60 = ?
c) 19 × 700 = ?
d) 205 × 400 = ?
e) 15 × 2,000 = ?
f) 32 × 5,000 = ?
ShowHide solutions
a) 26 × 30 = 26 × 3 × 10 = 78 × 10 = 780
b) 407 × 60 = 407 × 6 × 10 = 2,442 × 10 = 24,420
c) 19 × 700 = 19 × 7 × 100 = 133 × 100 = 13,300
d) 205 × 400 = 205 × 4 × 100 = 820 × 100 = 82,000
e) 15 × 2,000 = 15 × 2 × 1,000 = 30 × 1,000 = 30,000
f) 32 × 5,000 = 32 × 5 × 1,000 = 160 × 1,000 = 160,000
2. Find the product:
a) 35 × 20 = ?
b) 48 × 50 = ?
c) 72 × 300 = ?
d) 125 × 400 = ?
ShowHide solutions
a) 35 × 20 = 35 × 2 × 10 = 70 × 10 = 700
b) 48 × 50 = 48 × 5 × 10 = 240 × 10 = 2,400
c) 72 × 300 = 72 × 3 × 100 = 216 × 100 = 21,600
d) 125 × 400 = 125 × 4 × 100 = 500 × 100 = 50,000
Key Takeaways
- × 20 = × 2 × 10 (multiply by 2, then write one zero at the end)
- × 60 = × 6 × 10 (multiply by 6, then write one zero at the end)
- × 400 = × 4 × 100 (multiply by 4, then write two zeros at the end)
- × 600 = × 6 × 100 (multiply by 6, then write two zeros at the end)
- × 4,000 = × 4 × 1,000 (multiply by 4, then write three zeros at the end)
- You can multiply in any order: 43 × 20 = 43 × 2 × 10 = 43 × 10 × 2