It is easy to multiply by 20, because 20 is 2 times 10. It is easy to multiply by 10 and it is easy to multiply by 2. Th is is called multiplication by factors, because 10 and 2 are factors of 20 (20 = 10 × 2). So, to multiply any number by 20, you multiply it by 2 and then multiply the answer by 10, or, you could say, you double the
number and add a 0.
For instance, to multiply 7 by 20, you would double it (2 × 7 = 14) and then multiply your answer by 10 (14 × 10 = 140).
To multiply 32 by 20, you would double 32 (64) and then multiply by 10 (640).
Multiplying by 20 is easy because it is easy to multiply by 2 and it is easy to multiply by 10.
So, it is easy to use 20 as a reference number.
number and add a 0.
For instance, to multiply 7 by 20, you would double it (2 × 7 = 14) and then multiply your answer by 10 (14 × 10 = 140).
To multiply 32 by 20, you would double 32 (64) and then multiply by 10 (640).
Multiplying by 20 is easy because it is easy to multiply by 2 and it is easy to multiply by 10.
So, it is easy to use 20 as a reference number.
No comments:
Post a Comment