Finding the Fourth Proportional to 1,665.20, 2,498.16 and 690.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,665.20 : 2,498.16 = 690.78 : x
2. Step 2: Convert to fraction form
   1,665.20/2,498.16 = 690.78/x
3. Step 3: Cross multiply
   1,665.20x = 2,498.16 × 690.78
4. Step 4: Simplify right side
   1,665.20x = 1,725,678.96
5. Step 5: Solve for x
   x = 1,725,678.96/1,665.20
6. Step 6: Final answer
   x = 1,036.32