Divide Decimals

Dividing Decimals by Powers of Ten:

If you divide a decimal number by 10, the decimal point moves 1 place to make the number smaller
(for example 2345.6 ÷ 10 = 234.56).

If you divide a decimal number by 100, the decimal point moves 2 places to make the number smaller
(for example 2345.6 ÷ 100 = 23.456).

If you divide a decimal number by 1000, the decimal point moves 3 places to make the number smaller
(for example 2345.6 ÷ 1000 = 2.3456).



Dividing Decimals by Other Whole Numbers:

Example One - Price of Strawberries

Strawberries

3 kilograms of strawberries cost $19.65. What is the price of one kilogram?

Answer:
$19.65 ÷ 3 = $6.55

Questions - Price of Food

Q1. A dozen eggs (12 eggs) cost $5.16. What is the price of one egg?
Q2. 10 apples cost $4.90. What is the cost of one apple?
Q3. 5 bags of Persian Cotton Candy cost $24.25. What does one bag cost?

Answers
A1. 43 cents
A2. 49 cents
A3. $4.85

Dividing Decimals by Decimals:

Example Two - Injection Doses

Syringe

A glass vial contains 45.5 millilitres of medicine. Each injection requires 0.5 millilitres. How many injections can be given from one glass vial?

Answer:

= 45.5
0.5
= 455(Multiply both the numerator and the denominator by 10 to get rid of the decimal in the denominator.)
5

= 91 injections


Example Three - Smaller Injection Doses

Using the same-sized glass vial containing 45.5 millilitres of medicine, each injection has 0.05 millilitres. How many injections can be given from one glass vial?

Answer:

= 45.5
0.05
= 4550(Multiply both the numerator and the denominator by 100 to get rid of the decimal in the denominator.)
5

= 910 injections

Question - Ringtone Download

To download my favourite ringtones to my mobile 'phone costs $0.90 each. How many ringtones can I download if I have:
(a) $46.80
(b) $10.80
(c) $20.70?

Answers
(a) 52
(b) 12
(c) 23

Maths Fun - Dividing by Zero

Try dividing any number by zero on your calculator. The calculator will display and "Error" message because dividing by zero is impossible. However, we can approximate what number we could get if we divided a number such as "8" by numbers that are close to zero.

Use your calculator to work out the following:

What do you notice?