Finding the Fourth Proportional to 1,387.39, 1,915.02 and 856.43

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.39 : 1,915.02 = 856.43 : x
2. Step 2: Convert to fraction form
   1,387.39/1,915.02 = 856.43/x
3. Step 3: Cross multiply
   1,387.39x = 1,915.02 × 856.43
4. Step 4: Simplify right side
   1,387.39x = 1,640,081.16
5. Step 5: Solve for x
   x = 1,640,081.16/1,387.39
6. Step 6: Final answer
   x = 1,182.14