Construction NumeracyUsing Percentages in the Construction Industry Stonemasonry Department 2012
What is a Percentage? A percentage is a value used to express a number as a fraction of 100. A percentage is indicated by the symbol %. Can you think of where you see or use percentages on a daily basis? 20% DISCOUNT
Value Added Tax (VAT) Value Added Tax (VAT) is a tax levied on products sold or manufactured within the UK. It is currently set at 20% which means that for every £100 you spend, £20 is claimed by the Government. Value x 1.2 = Value including VAT for example £100 x 1.2 = £120 There are a number of different ways to calculate VAT but the easiest way is to establish the value of the items being bought and multiply them by 1.2. This is because 1.2 is 120% expressed as a decimal.
Value Added Tax (VAT) Can you calculate how much VAT @ 20% would be applied to the following amounts? £75.00 =£90.00 £53.00 =£63.60 £28.60 =£34.32 £94.22 =£113.04 £135.00 =£162.00 How many did you get correct? You should find that regardless of the amount, multiplying by 1.2 gives the value including VAT. The original values are known as the value excluding VAT.
Calculating Discounts Percentages are also commonly used to indicate discounts on products and materials. For example you might be told that bags of sand have 20% off normal retail price. This means that instead of paying 100% of the normal value for the sand you pay 80%. Without discount = £5.00 To apply the discount we multiply by 0.8 because 0.8 is the way to express 80% as a decimal. 5.00 x 0.8 = 4.00 With discount = £4.00
Calculating Discounts Can you apply discounts to the items shown below? ALL MIXERS 10% OFF DOORS 15% OFF OVERALLS 25% OFFRRP* £120.00 £315.00 £18.00Discounted £90.00 £267.75 £16.20
Calculating Wastage If you order the exact amount of materials for a job it is likely you wont have enough due to wastage and breakages. To avoid this we order additional materials, usually shown as a percentage. +10% 1000 blocks 1100 blocks In the example shown above there are 1000 mono-blocks required for a project. An additional 10% of required mono- blocks are ordered to allow for wastage and breakages. 1000 bricks x 1.1 = 1100 bricks
References The image on the second slide of this presentation was sourced from http://www.diabetic-dieting.com/food- label_files/Visual-Food-Label.jpg This image was made available under creative commons The image on the second slide of this presentation was sourced from http://psdhunter.com/psds/3633-progress- bar-by-milos-milikic.png This image was made available under creative commons
Developed by The Stonemasonry Department City of Glasgow College 2012