The speeds of two cars are in the ratio 7 : 8. If the second car covers 200 km in 5 hours (i.e., 40 km/h), find the speed of the first car (in km/h).

Introduction / Context:
Speed ratios scale actual speeds by a common factor. Once you identify the common factor from one car, you can compute the other car’s speed directly.

Given Data / Assumptions:

• Speed ratio (Car1 : Car2) = 7 : 8.
• Car2 speed = 200 / 5 = 40 km/h.

Concept / Approach:
If 8 parts correspond to 40 km/h, then 1 part is 40/8, and 7 parts (Car1) give the required speed.

Step-by-Step Solution:

Verification / Alternative check:
Proportion: 35 : 40 simplifies to 7 : 8, matching the ratio.

Why Other Options Are Wrong:
28, 25, 32, 40 km/h do not maintain the 7 : 8 proportion with a 40 km/h second car.

Common Pitfalls:
Confusing the mapping of “7” and “8” to the first/second car; not simplifying to get the correct scale factor.

Final Answer:
35 km/h