Finding the Fourth Proportional to 1,388.37, 1,915.60 and 828.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.37 : 1,915.60 = 828.61 : x
2. Step 2: Convert to fraction form
   1,388.37/1,915.60 = 828.61/x
3. Step 3: Cross multiply
   1,388.37x = 1,915.60 × 828.61
4. Step 4: Simplify right side
   1,388.37x = 1,587,281.17
5. Step 5: Solve for x
   x = 1,587,281.17/1,388.37
6. Step 6: Final answer
   x = 1,143.27