Finding the Fourth Proportional to 1,390.17, 1,918.47 and 800.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.17 : 1,918.47 = 800.76 : x
2. Step 2: Convert to fraction form
   1,390.17/1,918.47 = 800.76/x
3. Step 3: Cross multiply
   1,390.17x = 1,918.47 × 800.76
4. Step 4: Simplify right side
   1,390.17x = 1,536,234.04
5. Step 5: Solve for x
   x = 1,536,234.04/1,390.17
6. Step 6: Final answer
   x = 1,105.07