Finding the Fourth Proportional to 1,385.64, 1,911.78 and 861.48

Step by Step Solution

1. Step 1: Write the proportion equation
   1,385.64 : 1,911.78 = 861.48 : x
2. Step 2: Convert to fraction form
   1,385.64/1,911.78 = 861.48/x
3. Step 3: Cross multiply
   1,385.64x = 1,911.78 × 861.48
4. Step 4: Simplify right side
   1,385.64x = 1,646,960.23
5. Step 5: Solve for x
   x = 1,646,960.23/1,385.64
6. Step 6: Final answer
   x = 1,188.59