Finding the Fourth Proportional to 1,390.83, 1,918.51 and 866.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.83 : 1,918.51 = 866.76 : x
2. Step 2: Convert to fraction form
   1,390.83/1,918.51 = 866.76/x
3. Step 3: Cross multiply
   1,390.83x = 1,918.51 × 866.76
4. Step 4: Simplify right side
   1,390.83x = 1,662,887.73
5. Step 5: Solve for x
   x = 1,662,887.73/1,390.83
6. Step 6: Final answer
   x = 1,195.61