GCSE›AQA GCSE Maths›Mind mapsRates of ChangeAQA GCSE Maths: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsProportionDirect: X=kYX = kYX=kY, constant rateInverse: X=kYX = \frac{k}{Y}X=YkInverse means proportional to 1Y\frac{1}{Y}Y1Higher tier: construct the equationX=10X = 10X=10 at Y=2Y = 2Y=2 gives X=20YX = \frac{20}{Y}X=Y20GraphsStraight-line gradient is a constant rateConversion graph gradient is the exchange rateCurve: tangent gives instantaneous rateGradient is change in yyy over change in xxxCompound unitsSpeed = distance ÷ timeDensity = mass ÷ volumePressure = force ÷ areaAlso rates of pay and unit pricingRatesand unitskm/hg/cm³N/m²Unit conversionConvert between standard units freelyKnow metric conversion factorsImperial conversions are givenConvert both parts of a compound unitMoney ratesExchange rate is a multiplierBest buy: price per unitCombine with percentage change and interestDensity units: g/cm3\text{g/cm}^3g/cm3 or kg/m3\text{kg/m}^3kg/m3Exam tipsConvert top and bottom in km/h to m/sFind kkk using XY=kXY = kXY=k for inverseCompare rates across every option