Finding the Fourth Proportional to 1,389.84, 1,917.92 and 800.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.84 : 1,917.92 = 800.40 : x
2. Step 2: Convert to fraction form
   1,389.84/1,917.92 = 800.40/x
3. Step 3: Cross multiply
   1,389.84x = 1,917.92 × 800.40
4. Step 4: Simplify right side
   1,389.84x = 1,535,099.17
5. Step 5: Solve for x
   x = 1,535,099.17/1,389.84
6. Step 6: Final answer
   x = 1,104.52