Finding the Fourth Proportional to 1,158.78, 1,738.10 and 428.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,158.78 : 1,738.10 = 428.31 : x
2. Step 2: Convert to fraction form
   1,158.78/1,738.10 = 428.31/x
3. Step 3: Cross multiply
   1,158.78x = 1,738.10 × 428.31
4. Step 4: Simplify right side
   1,158.78x = 744,434.78
5. Step 5: Solve for x
   x = 744,434.78/1,158.78
6. Step 6: Final answer
   x = 642.43