Chapter 12
DIRECT AND INVERSE PROPORTIONS
DIRECT PROPORTION
(i) Two quantities x and y are said to be in direct proportion if whenever the value of x increases (or decreases) , then the value of y increases (or decreases ) in such a way that the ratio x / y remains constant.
(ii) When x and y are in direct proportion , we have
x1 / y1 = x2 / y2 = x3 / y3 ,etc
Example: More articles will cost more.
INVERSE PROPORTION
(i) Two quantities x and y are said to be inverse proportion if whenever the value of x increases (or decreases) , the value of y decreases (increases) in such a way that x * y remains constant.
(ii) When x and y are in inverses proportion , we have
x1 * y1 = x2 * y2 = x3 * y3 , and so on.
Example: More is the speed of a car , less is the time taken to cover a fixed distance.
Ex12B
