Finding the Fourth Proportional to 1,390.05, 1,917.47 and 830.34

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.05 : 1,917.47 = 830.34 : x
2. Step 2: Convert to fraction form
   1,390.05/1,917.47 = 830.34/x
3. Step 3: Cross multiply
   1,390.05x = 1,917.47 × 830.34
4. Step 4: Simplify right side
   1,390.05x = 1,592,154.12
5. Step 5: Solve for x
   x = 1,592,154.12/1,390.05
6. Step 6: Final answer
   x = 1,145.39