Question

Sushma has a road map with a scale of 1 cm representing 18 km. She drives on a road for 72 km. What would be her distance covered in the map?

Answer 1

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

let the distance represented on the map be x cm.

GIVEN:-

$\bold{Distance \;\;covered \;\; on\;\;road} \\\bold{Distance \;\; represent\;\;on\;\;map}\bold{\left[\begin{array}{ccc}18&72\\\\\\1&x\end{array}\right]}$.

The distances covered on road and represented on map are directly proportional to each other.

∴ 18/1 = 72/x

18x = 72

x = 72/18

x = 4

Hence, the distance represented on the map is 4 cm.

Answer 2

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

let the distance represented on the map be x cm.

The distances covered on road and represented on map are directly proportional to each other.

∴ 18/1 = 72/x

18x = 72

x = 72/18

x = 4

Hence, the distance represented on the map is 4 cm