TeachGCSEMathsFeetandMetres

TeachGCSEMathsFeetandMetres?ChristineCrispCertainimagesand/orphotosonthispresentationarethecopyrightedpropertyofJupiterImagesandarebeingusedwithpermissionunderlicense.Theseimagesand/orphotosmaynotbecopiedordownloadedwithoutpermissionfromJupiterImages

Heights,lengthsanddistancescanbemeasuredinimperialormetricunits.Animperialunitforlengththatisoftenusedisafoot.Mostpeoplesfeetarelessthanafootlong!Checkyourruler.Ifithasmarksupto30cmitisapproximately1foot.(I’llcallthisalongruler.)30cm≈1footTheeasiestwaytochangeunitsistofindthenumberof“bundles”(likewedidforkmandmiles).Ifyouuseoneoftheshortrulersitwillgiveyouhalfafoot.Thismeansapproximately.Iwilljustwrite=fromnowon.

e.g. Changethefollowingmetriclengthstofeet:30cm=1foot(a)90cm (b)75cm (c)3mSolutions:(a)90cm:90÷30=3numberof“bundles”in90:Check:Afootislongerthanacmsotherearefewerofthem.Each“bundle”is1footsotheansweris3feet.30cm=1foot(b)75cm:75÷30=2·5(or2andahalf)numberof“bundles”in75:75cmis2·5feetFewer!

(b)3m:30cm=1footWefirstneedtochangetocm:1metre=100centimetres3metres=300cmNowwecanchangetofeet:300÷30=10feetFeetareshorterthanmetressotherearemore.numberof“bundles”in300:

e.g. Change7feettometricunitsgivingtheanswerinmetresandcentimetres.30cm=1foot7?30=210cm100centimetres=1metre,soSolution:Rewritetheformulasothattheunitswearechangingfromcomefirst:1foot=30cm200centimetres=2metresThisleaves10cm,so,7feetis2m10cmWewant7feet,so7“bundles”:Weneedtochangetometres:

SUMMARYToconvertbetweenfeetandcentimetresuse30cm=1footArulerisagoodwaytoremembertheconversionfactorbetweencmandfeet.A“long”ruleris30cmor1foot.A“short”ruleris15cmor0·5f