Finding the Fourth Proportional to 1,388.22, 1,915.47 and 890.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.22 : 1,915.47 = 890.79 : x
2. Step 2: Convert to fraction form
   1,388.22/1,915.47 = 890.79/x
3. Step 3: Cross multiply
   1,388.22x = 1,915.47 × 890.79
4. Step 4: Simplify right side
   1,388.22x = 1,706,281.52
5. Step 5: Solve for x
   x = 1,706,281.52/1,388.22
6. Step 6: Final answer
   x = 1,229.11