"Question 9 A car takes 2 hours to reach a destination by travelling at the speed of 60 km/h. how long will it take when the car travels at the speed of 80 km/h?
Class 8 Direct and Inverse Proportions Page 214"
Answers
Inverse variation:
Two quantities x and y are said to vary inversely or indirectly if an increase in x causes a decrease in y and a decrease in X causes an increase in y in such a way that xy remains constant.
In other words x and y are said to vary indirectly if x y = k, where K is a positive constant.
In inverse Proportion
xy= k
x=k/y
So we can find value of k from known values, and then use the formula to calculate the unknown values
When two quantities x and y are in direct proportion (or vary directly) they are also written as x∝y.
When two quantities x and y are in inverse proportion (or vary inversely) they are also written as x∝ 1/y
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Solution:
Table is in the attachment
Let the time taken by the car to reach the destination with a speed of 80 km/hr, be x hours.
More the speed of the car, less will be the time taken
Hence, the speed of the car and the time taken by the car are inversely proportional to each other.
60 × 2 = 80× x
X= (60 x2)/ 80
X = (3 x 2 ) /4
X = 3/2 = 1 ½
X = 1 ½ hrs
hence,The time required by the car to reach the given destination is= 1 ½ hrs
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Hope this will help you....
