Finding the Fourth Proportional to 1,076.78, 1,615.83 and 427.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,076.78 : 1,615.83 = 427.57 : x
2. Step 2: Convert to fraction form
   1,076.78/1,615.83 = 427.57/x
3. Step 3: Cross multiply
   1,076.78x = 1,615.83 × 427.57
4. Step 4: Simplify right side
   1,076.78x = 690,880.43
5. Step 5: Solve for x
   x = 690,880.43/1,076.78
6. Step 6: Final answer
   x = 641.62