Multiplication of decimals by a whole number

Multiplying whole numbers by decimals

A method can be described as follows:

• Temporarily ignore the decimal point and multiply the number.
• Note that the number of decimal places in the answer must be the same as the number of decimal places in the original number.

Therefore for 75.5 × 3, the steps are as follows:

1 755 × 3 = 2265.

2 Number of decimal places is one. Hence

75.5 × 3 = 226.5.

Question 4

a A bag of sand weighs 25.6 kg. How much will 7 identical bags of sand weigh?
kg  

b Nine identical rods each have length 1.3 m. If they are laid end to end what is the total length?
m  

Multiplying by powers of 10