Following are the car parking charges …

Direct variation:

If two quantities increase or decrease together in such a
manner that the ratio of their corresponding values remain constant, we say  that the two quantities vary  directly.

In other words x and y are said to vary directly if X/y = k
, where k is a positive constant.

In direct Proportion

x/y= k

x=ky

So we can find value of k from known values, and then use the
formula to calculate the unknown values

 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:

Let the charges be x1 , x2, x3, x4

x1= 60/4= 15

X2= 100/8= 12.50

X3=140/12= 11.67

X4= 180/24= 7.50

x1 ≠ x2 ≠ x3 ≠ x4

Here, The charges per hour are not same ,
Hence the parking charges are not in direct proportion to the parking time.