Finding the Fourth Proportional to 1,139.78, 1,709.98 and 490.34

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.78 : 1,709.98 = 490.34 : x
2. Step 2: Convert to fraction form
   1,139.78/1,709.98 = 490.34/x
3. Step 3: Cross multiply
   1,139.78x = 1,709.98 × 490.34
4. Step 4: Simplify right side
   1,139.78x = 838,471.59
5. Step 5: Solve for x
   x = 838,471.59/1,139.78
6. Step 6: Final answer
   x = 735.64