Determine which set of ratios forms a proportion.
1. 9:10, 45:40
2. 1:16, 3:18
3. 1:8, 2:18
4. 5:10, 20:40
4. 5:10, 20:40
In this set, if you simplify the ratios by dividing both numbers by 10, you get:
5:10 simplifies to 1:2
20:40 simplifies to 1:2
Therefore, the set of ratios 5:10 and 20:40 form a proportion.