Category : 8th Class
Direct and Inverse Proportions
A method in which the value of a quantity is first obtained to find the value of any required quantity is called unitary method.
(i) Two quantities x and y are said to be in direct proportion if they increase (decrease) together in such a manner that the ratio of their corresponding values remains constant.
(ii) That is, if \[\frac{X}{Y}=K\] [k is a positive number], then x and y are said to vary directly. In such
(a) As the number of articles increases, their cost increases. Cost is directly proportional to the number of articles.
(b) The more the number of men, the more work is done in a given time. Work done is directly proportional to the number of men working at it.
(i) Two quantities x and y are said to be in inverse proportion if an increase in x causes a proportional decrease in y (and vice-versa) in such a manner that the product of their corresponding values remains constant.
(ii) That is, if xy = k, then x and y are said to vary inversely. In this case, if \[{{\operatorname{y}}_{1}}\,and\,{{y}_{2}}\]are
\[{{\operatorname{x}}_{1}}{{y}_{1}}={{x}_{2}}{{y}_{2}}\,or\,\frac{{{x}_{1}}}{{{x}_{2}}}=\frac{{{y}_{2}}}{{{y}_{1}}}\].
(i) The more men employed, the less time it takes to complete a given work. The time taken to finish a work is inversely proportional to the number of persons working at it.
(ii) If speed of car is increased, time taken to cover a given distance decreases. The time taken by any vehicle in covering a certain distance is inversely proportional to the speed of the vehicle.
You need to login to perform this action.
You will be redirected in
3 sec