Finding the Fourth Proportional to 2,085.78, 3,129.54 and 915.18

Step by Step Solution

1. Step 1: Write the proportion equation
   2,085.78 : 3,129.54 = 915.18 : x
2. Step 2: Convert to fraction form
   2,085.78/3,129.54 = 915.18/x
3. Step 3: Cross multiply
   2,085.78x = 3,129.54 × 915.18
4. Step 4: Simplify right side
   2,085.78x = 2,864,095.85
5. Step 5: Solve for x
   x = 2,864,095.85/2,085.78
6. Step 6: Final answer
   x = 1,373.15