Finding the Fourth Proportional to 1,387.45, 1,913.85 and 915.35

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.45 : 1,913.85 = 915.35 : x
2. Step 2: Convert to fraction form
   1,387.45/1,913.85 = 915.35/x
3. Step 3: Cross multiply
   1,387.45x = 1,913.85 × 915.35
4. Step 4: Simplify right side
   1,387.45x = 1,751,846.37
5. Step 5: Solve for x
   x = 1,751,846.37/1,387.45
6. Step 6: Final answer
   x = 1,262.63