Finding the Fourth Proportional to 1,388.48, 1,915.33 and 890.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.48 : 1,915.33 = 890.55 : x
2. Step 2: Convert to fraction form
   1,388.48/1,915.33 = 890.55/x
3. Step 3: Cross multiply
   1,388.48x = 1,915.33 × 890.55
4. Step 4: Simplify right side
   1,388.48x = 1,705,697.13
5. Step 5: Solve for x
   x = 1,705,697.13/1,388.48
6. Step 6: Final answer
   x = 1,228.46