G S Rehill's Interactive Maths Software Series - "Building a Strong Foundation in Mathematics" from mathsteacher.com.au.

 

Year 7 Interactive Maths - Second Edition


Multiplication of a Decimal by a Multiple of a Power of Ten

Consider the multiplication 6.4 × 2 ×10.

Move the decimal point 1 place to the right.

This suggests that:

  • To multiply a decimal by a multiple of a power of 10, we can first multiply the decimal by the multiple; and then multiply by the power of 10.
  • Multiplying by a power of 10 requires moving the decimal point one place to the right for each zero in the power of 10.


Example 21

Calculate 9.4 × 30.

Solution:

Move the decimal point 1 place to the right.


Alternative way:

Note that there is 1 decimal place in the number being multiplied and so there is 1 decimal place in the answer.


Example 22

Calculate 0.84 × 7000.

Solution:

Move the decimal point 3 places to the right.


Alternative way:

Note that there are 2 decimal places in the number being multiplied and so there are 2 decimal places in the answer.

 

Study Another Topic in Chapter 6: Decimals

Decimals ] Representation of Decimals on a Number Line ] Comparing Decimals ] Addition of Decimals ] Subtraction of Decimals ] Multiplication of Decimals ] Multiplication of a Decimal by a Power of Ten ] [ Multiplication of a Decimal by a Multiple of a Power of Ten ] Multiplication of a Decimal Number by another Decimal Number ] Division of a Decimal by a Whole Number ] Division of a Decimal by a Power of a Ten ] Division of a Decimal by a Multiple of a Power of Ten ] Division of a Decimal by another Decimal ] Rounding Off ] Recurring Decimals ] Problem Solving Unit ] Symbols ] Index ]

 

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