Finding the Fourth Proportional to 2,085.31, 3,128.93 and 915.16

Step by Step Solution

1. Step 1: Write the proportion equation
   2,085.31 : 3,128.93 = 915.16 : x
2. Step 2: Convert to fraction form
   2,085.31/3,128.93 = 915.16/x
3. Step 3: Cross multiply
   2,085.31x = 3,128.93 × 915.16
4. Step 4: Simplify right side
   2,085.31x = 2,863,471.58
5. Step 5: Solve for x
   x = 2,863,471.58/2,085.31
6. Step 6: Final answer
   x = 1,373.16