BACCALAURÉAT GÉNÉRAL ET TECHNOLOGIQUE SESSION 2009 ÉPREUVE SPÉCIFIQUE MENTION « SECTION EUROPÉENNE OU DE LANGUE ORIENTALE »
Académies de Paris-Créteil-Versailles
Binôme : Anglais / Mathématiques Sujet 4 RATIOS AND PERCENTAGES The first part of this page is a summary that can help you to do the exercise.
Ratios are used to compare similar quantities. For example, “the ratio of 4g to 12g” means “4g compared with 12g”, which can be simplified, i.e. expressed in smaller whole numbers, as “the ratio of 1g to 3g”, which itself can be expressed, getting rid of the units as “the ratio of 1 to 3”. It is denoted by 1 : 3. The scales of maps are usually given as ratios in the form 1 : n. Example: divide £60 between two people A and B in the ratio 5 : 7. First you look for the total number of shares or parts. Here there are 5 + 7 = 12 parts altogether. 7 5 : 60 × 7 = 25 : 35 = £25 : £35. Then 5 : 7 = 5 : = 60 × 12 12 12 12 A receives £25 and B receives £35. EXERCISE: 1. Two varieties of tea, ‘High Blend’ and ‘Normal Blend’, are made by mixing Grade A leaves and Grade B leaves. (i) In High Blend, the ratio of the masses of Grade A leaves to Grade B leaves is 3 : 2. Find the mass of Grade A leaves used in making 250 g of High Blend. (ii) 1 kg of Normal Blend is made by using 450 g of Grade A leaves. Find, in its simplest form, the ratio of the masses of Grade A to Grade B leaves in Normal Blend. Give your answer in the form m : n, where m and n are integers. (iii) 250 g of High Blend is mixed with 1 kg of Normal Blend. Calculate the percentage of the mass of this mixture that consists of Grade A leaves. 2. During a sale, packets of tea were sold 20% less than the price displayed on their labels. Elizabeth and Peter each bought a packet of tea in the sale. (i) Elizabeth’s packet had a label price of £4.50.How much did she pay? (ii) Peter paid £6.20 for his packet. Calculate the price displayed on its label.
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