What do we mean when we say two quantities are inversely proportional ?It means that if:one of them doubles,the other one halves.one of them x3,the other one 3.one of them x4,the other one 4.one of them 2,the other one x2.one of them 10,the other one x10.Can you give an example of inversely proportional quantities from every day life?

The Civic Centre is to be painted, so they call a firm of decorators. If this firm provide:1 decorator 2 decorators3 decorators4 decorators5 decorators6 decorators10 decorators12 decorators15 decorators20 decorators30 decorators60 decorators120 decoratorswill take 60 days for the jobwill take 30 days for the jobwill take 20 days for the jobwill take 15 days for the jobwill take 12 days for the jobwill take 10 days for the jobwill take 6 days for the jobwill take 5 days for the jobwill take 4 days for the jobwill take 3 days for the jobwill take 2 days for the jobwill take 1 day for the jobwill take day for the job 1 x 60 2 x 30 3 x 20 4 x 15 5 x 12 6 x 1010 x 612 x 515 x 420 x 330 x 260 x 1120 x

INVERSELY PROPORTIONAL QUANTITIES

One increases at the same rate as the other one decreases.

More formally:

Two quantities are inversely proportional if their product remains constant.

15 factory workers produce a car in 12 days.How many days do 10 workers take to produce the same car?How many workers do we need to produce a car in 5 days?Factory Workersworkersdaysx22Inversely Proportionalworkersxdays=constant15x12=18018010=1810 workers take 18 days1805=3636 workers take 5 days

6 water pumps fill in a water tank in 15 hours.If one of these pumps is not working, how long will the 5 water pumps take?If we want the tank filled in in 9 hours how many of these water pumps must we have?Water Pumpspumpshoursx22Inversely Proportionalpumpsxhours=constant6x15=90905=185 water pumps will take 18 hours909=10To fill the tank in 9 hours we need 10 water pumps

A circular flower bed has space for 120 plants, placed 36 cm apart.If we place them 40 cm apart how many plants can we fit?If we need to fit 150 plants how far apart must we place them?Flower Bedsplantsspacingx22Inversely Proportionalplantsxspacing=constant120x36=4320432040=108If we place them 40 cm apart we can fit 108 plants4320150=28.8In order to fit 150 plants we must place them 28.8 cm apart

When full, a watering trough provides enough water to last 24 horses for 5 days.How many days will the same trough, when full, last 15 horses?horsesdaysx22Inversely Proportionalhorsexdays=constant24x5=12012015=8The watering trough will last 15 horses for 8 days