Answer:
9/10
Explanation:
You would first find the GCF. 36 factors: 1, 2, 3, 4, 6, 9, 12, 18, 36. 40 factors: 1, 2, 4, 5, 8, 10, 20, 40. The GCF would be 4, so divide by 4 on both sides and you would have the ratio 9 hr.: 10 hr. If using part to whole it would be 9/10.
Hope this helps