Rashmi 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?

Hint: To solve this question, we can use the unitary method as for any specific value corresponding to some other value, so that it can be change to a unit value corresponds to what value, effectively we all can multiply with the unit value with the number of times according to the question.

Complete step-by-step answer:
Given, 1 cm on the road map represents 18 km in actual.
Use unitary method now,
18 km in actual is 1 cm on the map.
1 km in actual will be $\dfrac{1}{{18}}{\text{cm}}$ on the map.
Therefore,
72 km in actual will be equal to $72 \times \dfrac{1}{{18}}$ which will be 4 cm on the map.
Therefore, Rashmi has covered a distance of 4 cm on the road map.

Note: This question can also be solved with the help of the concept of direct proportion, It can be observed that when the value of something is increasing or decreasing, simultaneously the associated value also increases or decreases in such a way that the ratio these two quantities does not change; it remains constant. We say that these two quantities are in direct proportion.