IGCSE Revision Lesson 1 I can carry out calculations involving reverse percentages, e.g. finding the cost price given the selling price and the percentage profit I can obtain appropriate upper and lower bounds to solutions of simple problems (e.g. the calculation of the perimeter or the area of a rectangle) given data to a specified accuracy I can use language, notation and Venn diagrams to describe sets and represent relationships between sets (see syllabus for list)

Venn Diagrams and Set Notation Set – a collection of objects, usually that satisfy a certain rule.

Venn Diagrams and Set Notation True or false: n(A) = 10 False – n(A) = 10+2=12 n(A ∩ B) = 2 True n(AuB) = 22 False – n(AuB) = n(A) + n(B) – n(A ∩ B ) n(A’) = 17 False - n(A’) = 15

Venn Diagrams and Set Notation A = {2, 3, 5, 7, 9} B = {1, 2, 3, 5, 8} Complete the Venn diagram, starting from the middle. True or false: {2, 3, 4} ≤ A False: 4 A (A n B) ≤ { 2, 3, 5, 7} True (A’ n B) = {1, 8, 9} False - (A’ n B’) = {1, 8}

Reverse Percentage Change % increase 50% decrease 2% decrease 20% increase % decrease 95% decrease 0.5% increase 17.5% increase

Reverse Percentage Change In a clearance sale, an iPod costs $25. How much would it cost normally? X$25multiplied by 0.25

Reverse Percentage Change I need $20,000 in five years’ time to buy a new bike. I can get 6% interest each year in a bank account. How much do I need to invest now? 2014: $20,000 X$20,000multiplied by

Reverse Percentage Change In the UK, VAT (‘sales tax’) is 15%. A computer costs 400 including tax. How much would it cost before tax?

Upper and Lower Bounds State the possible range of these values 30 to nearest ≤ x < to nearest 1dp 4.25 ≤ x < to nearest ≤ x < to nearest 2sf 64.5 ≤ x < to nearest ≤ x < dp – decimal place sf – significant figure

Upper and Lower Bounds In this rectangle, the sides are measured to the nearest cm. What is the smallest possible exact area? 13cm 20cm

Upper and Lower Bounds On 31 st May I will run the SP marathon. The distance I will run is 42km to the nearest km. I will run at 10km per hour to the nearest km/hr. What is the longest amount of time it would take me?

Practice questions Sets Page 39, Student Asst 4, Q2, 3, 4 Reverse percentage change Page 77, Q3, 4, 5, 6 Limits of accuracy Page 49, Q1, 5, 6