What is the difference between direct and inverse proportion and how do I know which to use? What are real-life examples please?
1 Answer
You have to consider which quantities are being compared and use common sense to decide how they relate to each other.
Explanation:
Both direct and indirect proportion are a comparison between two quantities (usually with different units).
In a direct proportion, as one quantity increases, the other also increases.
Examples would include:
If you buy more packets, it will cost more money.
If you have further to travel it will take more time.
If more people are to be fed, more food will be need.
If more people are to be transported, more cars/buses are needed.
More petrol is needed for longer distances.
Bigger area of floor will require more tiles/paint/wood.
A longer distance will need more paces to cover.
More dresses to be made will require more material.
In a direct proportion, the ratio between matching quantities stays the same if they are divided. (They form equivalent fractions).
In an indirect (or inverse) proportion, as one quantity increases, the other decreases.
If more people share a task, it will be done in less time.
Travelling at a faster speed means a trip will take less time.
If sugar is packed in smaller packets, more packets will be needed for the same mass.
For the same amount of money, a small parcel can be sent further than a bigger parcel.
If more people are being fed, food will be used up quicker.
For a fixed amount of money, as the price of presents increases, fewer can be bought.
Walking with longer strides means fewer paces are needed.
In an inverse proportion, the product of the matching quantities stays the same.
A hyperbola is the graph of inverse proportion.
Hope this helps?
