Finding the Fourth Proportional to 1,390.27, 1,917.87 and 830.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.27 : 1,917.87 = 830.56 : x
2. Step 2: Convert to fraction form
   1,390.27/1,917.87 = 830.56/x
3. Step 3: Cross multiply
   1,390.27x = 1,917.87 × 830.56
4. Step 4: Simplify right side
   1,390.27x = 1,592,906.11
5. Step 5: Solve for x
   x = 1,592,906.11/1,390.27
6. Step 6: Final answer
   x = 1,145.75