Finding the Fourth Proportional to 1,120.52, 1,681.55 and 390.10

Step by Step Solution

1. Step 1: Write the proportion equation
   1,120.52 : 1,681.55 = 390.10 : x
2. Step 2: Convert to fraction form
   1,120.52/1,681.55 = 390.10/x
3. Step 3: Cross multiply
   1,120.52x = 1,681.55 × 390.10
4. Step 4: Simplify right side
   1,120.52x = 655,962.30
5. Step 5: Solve for x
   x = 655,962.30/1,120.52
6. Step 6: Final answer
   x = 585.41