Decorating a room-


Harry is changing his room colours.


5 ltr

2.5 ltr

1 ltr


Work out the cheapest
prices for 



ltr of paint



Average cost per litre 
(to the nearest penny)


What would it cost for


rooms the same size



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How to solve the decorating problem

Find the row in the table that contains the information you will need,.
  blue   21.00   12.00    6.00      
  So  to find the cheapest cost of
14.5 litres of blue paint you need to find the combination of tin sizes that has the smallest number of tins for  14.5 litres of blue, start with the largest tin size first to see how many tins you will need of that size.

  Using division 5 goes into 14.5 twice with 4.5 litres left to buy (remember you can only buy whole tins of paint), so you will need to buy more tins of paint in smaller sizes,

  - Start with the largest sized tins as they are better value for money in this case .

The next sized tin down is 2.5 litres, as Harry still needs 4.5 litres of paint, you can see he will need one 2.5 tin of paint which then leaves him with 2 more litres fo buy, so the total amount of tins he needs to get the cheapest price is 2 x 5ltr tins, 1 x 2.5ltr tin and 2 x 1ltr tins, your final calculation should look something like this one below .

                                     (2 x 21.00) + (1 x 12.00) + (2 x 6.00)
                                 =  42.00 + 12.00 + 12.00
                                 =  66

to  keep things tidy try putting brackets around each section of the initial calculation (BODMAS), this will help to stop confusion when doing the calculations.
To find the average cost per litre you just divide the total cost of the paint needed 66.00 by the amount of litres you have bought 14.5l using long division (Note you only need to go to 2 d.p as this represents pence)

  At this point 14.5 does not go into 8 so you now need to put in a decimal point and a place holding 0, so that you can carry out the the next step of the calculation as shown below.

The complete calculation should look like this 

 So you now have digit values for the whole, tenths and hundredths columns, which is what you need to give your answer in pounds and pence (to 2 d.p).

So you add up all the  values of the place columns to get an answer of 4.55 per ltr.


Practice answering some more questions using your calculator.

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= 0