Note that 101 = 505 = 808 = 10010
Therefore, the number of pens and their cost are in direct variation.
Eg. 2:
Let the cost of one candy be 5 units.
Then, the cost of two candies will be 10 units.
And the cost of three candies will be 15 units.
From the above example it is clear that as the number of candies increases, the cost
also increases and hence in this case the candies and the cost are said to be in direct
variation.
The idea may be made simpler by taking a real life experience. Assume that the child
is buying some chocolates from a shop. The more the number of chocolates he/she
buys, more the money he/she has to pay. Less the number of chocolates he/she buys,
less the money he/she has to pay and hence the number of chocolates bought and the
money paid are in direct variation.
- Inverse variation
If two quantities uniformly vary such that when one of them increases the other
decreases and vice versa then the quantities are said to be in inverse variation.
Eg. : Supposing a person wants to walk from a place A to B. Let us assume that for a
normal person this journey takes 30 minutes.
Once started, if the person walks faster than a normal person then the time decreases.
And if the person walks slower than a normal person then the time will be more than
30 minutes, that is, the time increases. Thus when one quantity increases the other
decreases and when one decreases the other increases, thus forming an inverse variation.
Here the speed in walking and the time taken are showing inverse variation.
