A distance of 68 km is represented on a map by 1.7 cm. What distance is represented by 8.5 cm on the same map?

Given:

Map distance 1.7 cm = Actual distance 68 km

Map distance 8.5 cm = ?

Let actual distance for 8.5 cm = x km

Ratio of map distances : Ratio of actual distances

1.7 : 8.5 :: 68 : x

By the rule: Product of Extremes = Product of Means:

1.7 x x = 8.5 x 68

⇒ x = $\dfrac{8.5 \times 68}{1.7}$

⇒ x = 5 x 68

⇒ x = 340

Hence, the distance represented is 340 km.