Example # 1
Find the procuct mentally. 40 x 7,000
1. Find the basic multiplication fact 4 x 7 = 28
2. Count the number of zeros in each factor.
40 - one zero
7,000 - three zeros Total of 4 zeros
3. Write the zeros to the right of the product in step 1.
280,000
Answer 280,000
Example #2
Find the product mentally 21 x 102
1. Write 102 without exponents 102 = 100 The exponent tells you the number of zeros in the power of 10.
2. Find the basic multiplication fact. 21 x 1 = 21
3. Count the number of zeroes in the factors - total of 2 zeros
4. Write the zeroes to the right of the product 2,100
Short cut - Look at the exponent. In this case it is 2. This tells you the number of zeros in the power of 10. You are multiplying 21 by a power of 10 with 2 zeros.
Vocabulary
102 This number is read as 10 to the power of 2 or 10 squared.
10 is the base. The exponent indicates how many times the base is used as a factor.
102 = 10 x 10
103 = 10 x10 x 10
