Finding the Fourth Proportional to 1,387.40, 1,913.82 and 915.38

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.40 : 1,913.82 = 915.38 : x
2. Step 2: Convert to fraction form
   1,387.40/1,913.82 = 915.38/x
3. Step 3: Cross multiply
   1,387.40x = 1,913.82 × 915.38
4. Step 4: Simplify right side
   1,387.40x = 1,751,872.55
5. Step 5: Solve for x
   x = 1,751,872.55/1,387.40
6. Step 6: Final answer
   x = 1,262.70