Finding the Fourth Proportional to 1,099.86, 1,648.17 and 405.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,099.86 : 1,648.17 = 405.78 : x
2. Step 2: Convert to fraction form
   1,099.86/1,648.17 = 405.78/x
3. Step 3: Cross multiply
   1,099.86x = 1,648.17 × 405.78
4. Step 4: Simplify right side
   1,099.86x = 668,794.42
5. Step 5: Solve for x
   x = 668,794.42/1,099.86
6. Step 6: Final answer
   x = 608.07