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GCSE Maths Starter 13

GCSE Maths Starter 13. Write down the reciprocal of 3 Write 42 as a product of its prime factors Find the perimeter and the shaded area of the shape below. Expand: 5a(3a+2). Lesson 13 Ratio Mathswatch clip (61/94). To simplify a ratio ( Grade D )

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GCSE Maths Starter 13

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  1. GCSE Maths Starter 13 Write down the reciprocal of 3 Write 42 as a product of its prime factors Find the perimeter and the shaded area of the shape below. Expand: 5a(3a+2)

  2. Lesson 13 RatioMathswatch clip (61/94). To simplify a ratio (Grade D ) To solve ratio problems using the unitary method (Grade D)

  3. I like simple cakes made only out of flour and sugar . I mix it using a ratio of 2 : 1 But now my cake is 4 : 2 !!! But the cake will not be big enough ! Both ratios are equivalent. They can be simplified in the same way as fractions are simplified. But the cake tastes exactly the same ! Two goes into both 4 and 2 Repeat the process ! 2 : 1 2 Sugar Flour 4 : 2 1 :

  4. I’m going to try a cake using flour and sugar in a ratio of 2 : 3 But now my cake has used a ratio of 4 : 6 !!! But the cake will not be big enough ! But the cake will taste exactly the same ! 2 : 3 is a simplified version of 4 : 6 Repeat the process. Two goes into 4 and 6 : 2 3 Sugar Flour 2 4 6 3

  5. Lesson 13 RatioMathswatch clip (61/94). Write the following ratios in their simplest form. 1 : 2 2 : 3 1 : 3 1) 4 : 8 2) 8 : 12 3) 4 : 12 4) 6 : 9 5) 10 : 20 6) 8 : 10 7) 2 : 8 8) 14 : 6 9) 30 : 20 10) 7 : 21 11) 8 : 22 12) 9 : 6 2 : 3 1 : 2 4 : 5 1 : 4 7 : 3 3 : 2 1 : 3 4 : 11 3 : 2

  6. Lesson 13 RatioMathswatch clip (61/94). • 1. Helen has 16 DVDs and 24 videos. • Write down the ratio of the number of DVDs to the number of videos.Give your ratio in its simplest form. • 2. There are 40 students on a school trip. 12 of the students are girls. The rest are boys. • Find the ratio of the number of girls to the number of boys. Give your ratio in its simplest form. • There are 50 sweets in a packet.24 of the sweets are mints.The rest of the sweets are toffees. • Write down the ratio of the number of mints to the number of toffees.Give your ratio in its simplest form.

  7. Lesson 13 RatioMathswatch clip (61/94). • 1. Helen has 16 DVDs and 24 videos. • Write down the ratio of the number of DVDs to the number of videos.Give your ratio in its simplest form. 16:24 = 2:3 • 2. There are 40 students on a school trip. 12 of the students are girls. The rest are boys. • Find the ratio of the number of girls to the number of boys. Give your ratio in its simplest form. 12:28 = 3:7 • There are 50 sweets in a packet.24 of the sweets are mints.The rest of the sweets are toffees. • Write down the ratio of the number of mints to the number of toffees.Give your ratio in its simplest form. 24:26 = 12:13

  8. Divide £40 in the ratio 2 : 3. A ratio is made up of parts. Dividing in a given ratio We can write the ratio 2 : 3 as 2 parts : 3 parts The total number of parts is 2 parts + 3 parts = 5 parts We need to divide £40 by the total number of parts. £40 ÷ 5 = £8

  9. Divide £40 in the ratio 2 : 3. and 3 parts = Each part is worth £8 so Dividing in a given ratio 2 parts = 2 × £8 = £16 3 × £8 = £24 £40 divided in the ratio 2 : 3 is £16 : £24 Always check that the parts add up to the original amount. £16 + £24 = £40

  10. A citrus twist cocktail contains orange juice, lemon juice and lime juice in the ratio 6 : 3 : 1. How much of each type of juice is contained in 750 ml of the cocktail? Dividing in a given ratio First, find the total number of parts in the ratio. 6 parts + 3 parts + 1 part = 10 parts Next, divide 750 ml by the total number of parts. 750 ml ÷ 10 = 75 ml

  11. A citrus twist cocktail contains orange juice, lemon juice and lime juice in the ratio 6 : 3 : 1. How much of each type of juice is contained in 750 ml of the cocktail? Dividing in a given ratio Each part is worth 75 ml so, 6 parts of orange juice = 6 × 75 ml = 450 ml 3 parts of lemon juice = 3 × 75 ml = 225 ml 1 part of lime juice = 75 ml Check that the parts add up to 750 ml. 450 ml + 225 ml + 75 ml = 750 ml

  12. Lesson 13 RatioMathswatch clip (61/94). Share in the given ratios • Share £400 between Courtney and Adele in the ratio 2:3 • Share £280 between April and Jack in the ratio 2:5 • Share £500 between Molly and Toni in the ratio 3:7 Extension work • Share £240 between Brad and Emma and Louis in the ratio 3:5:12 • Share £600 between Kera, Chloe and Raven in the ratio 1:5:6 • Share £5 between Jake, Adele and Lucretia in the ratio 7:10:8

  13. Lesson 13 RatioMathswatch clip (61/94). Answers • Courtney = £160 and Adele = £240 • April = £80 and Jack = £200 • Molly =£150 and Toni = £350 Extension work • Brad = £36 Emma = £60 Louis = £144 • Kera = £50 Chloe = £250 Raven = £300 • Jake = £1.40 Adele = £2.00 Lucretia = £1.60

  14. Lesson 13 RatioMathswatch clip (61/94). Exam questions

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