Finding the Fourth Proportional to 1,389.78, 1,917.76 and 830.14

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.78 : 1,917.76 = 830.14 : x
2. Step 2: Convert to fraction form
   1,389.78/1,917.76 = 830.14/x
3. Step 3: Cross multiply
   1,389.78x = 1,917.76 × 830.14
4. Step 4: Simplify right side
   1,389.78x = 1,592,009.29
5. Step 5: Solve for x
   x = 1,592,009.29/1,389.78
6. Step 6: Final answer
   x = 1,145.51