Running at 5/4 of his usual speed, an athlete improves his timing by 10 minutes. The time he usually takes to run the same distance is:

Question: Running at 5/4 of his usual speed, an athlete improves his timing by 10 minutes. The time he usually takes to run the same distance is:

Solution:
When the athlete walks at 5/4 of his usual speed then he takes 4/5 of his usual time and he saves 10 minutes.

Now
→ Usual time - (4/5) × usual time = 10 minutes
→ Usual time {1 - (4/5)} = 10 minutes
→ (1/5) × Usual time = 10 minutes
→ Usual time = 50 minutes.