Finding the Fourth Proportional to 1,388.30, 1,915.25 and 828.63

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.30 : 1,915.25 = 828.63 : x
2. Step 2: Convert to fraction form
   1,388.30/1,915.25 = 828.63/x
3. Step 3: Cross multiply
   1,388.30x = 1,915.25 × 828.63
4. Step 4: Simplify right side
   1,388.30x = 1,587,029.46
5. Step 5: Solve for x
   x = 1,587,029.46/1,388.30
6. Step 6: Final answer
   x = 1,143.15