If the price of 12 Eggs is Rs.96, how many eggs can be bought with Rs.80? (ans. 10 eggs)

Solution: We see that as the amount decreases the number of toys also decreases. So it is a direct proportion.

So the arrows will be drawn in the same direction, no matter if drawn in a upwards or downwards direction. But it is better to draw an arrow starting from ｘ

Now the the proportion will become

 X  : 12  :: 80 :  96

As we know that the product of mean is equal to product of extreme of a proportion we have

 X  ï½˜ 96  = 12 ï½˜  80

or

 X   =  `\frac{12 ｘ 80}{96}`

by simplifying 

 X   =  10 eggs

Thus, 10 eggs can be bought with Rs.80