Finding the Fourth Proportional to 1,387.98, 1,914.15 and 915.48

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.98 : 1,914.15 = 915.48 : x
2. Step 2: Convert to fraction form
   1,387.98/1,914.15 = 915.48/x
3. Step 3: Cross multiply
   1,387.98x = 1,914.15 × 915.48
4. Step 4: Simplify right side
   1,387.98x = 1,752,366.04
5. Step 5: Solve for x
   x = 1,752,366.04/1,387.98
6. Step 6: Final answer
   x = 1,262.53