Finding the Fourth Proportional to 1,388.34, 1,915.31 and 828.63

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.34 : 1,915.31 = 828.63 : x
2. Step 2: Convert to fraction form
   1,388.34/1,915.31 = 828.63/x
3. Step 3: Cross multiply
   1,388.34x = 1,915.31 × 828.63
4. Step 4: Simplify right side
   1,388.34x = 1,587,085.40
5. Step 5: Solve for x
   x = 1,587,085.40/1,388.34
6. Step 6: Final answer
   x = 1,143.15