Finding the Fourth Proportional to 1,380.91, 1,906.16 and 915.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.91 : 1,906.16 = 915.31 : x
2. Step 2: Convert to fraction form
   1,380.91/1,906.16 = 915.31/x
3. Step 3: Cross multiply
   1,380.91x = 1,906.16 × 915.31
4. Step 4: Simplify right side
   1,380.91x = 1,744,727.31
5. Step 5: Solve for x
   x = 1,744,727.31/1,380.91
6. Step 6: Final answer
   x = 1,263.46