Finding the Fourth Proportional to 1,665.20, 2,495.10 and 1,389.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,665.20 : 2,495.10 = 1,389.80 : x
2. Step 2: Convert to fraction form
   1,665.20/2,495.10 = 1,389.80/x
3. Step 3: Cross multiply
   1,665.20x = 2,495.10 × 1,389.80
4. Step 4: Simplify right side
   1,665.20x = 3,467,689.98
5. Step 5: Solve for x
   x = 3,467,689.98/1,665.20
6. Step 6: Final answer
   x = 2,082.45