Finding the Fourth Proportional to 1,388.62, 1,915.41 and 1,056.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.62 : 1,915.41 = 1,056.31 : x
2. Step 2: Convert to fraction form
   1,388.62/1,915.41 = 1,056.31/x
3. Step 3: Cross multiply
   1,388.62x = 1,915.41 × 1,056.31
4. Step 4: Simplify right side
   1,388.62x = 2,023,266.24
5. Step 5: Solve for x
   x = 2,023,266.24/1,388.62
6. Step 6: Final answer
   x = 1,457.04