Finding the Fourth Proportional to 1,388.27, 1,915.65 and 790.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.27 : 1,915.65 = 790.55 : x
2. Step 2: Convert to fraction form
   1,388.27/1,915.65 = 790.55/x
3. Step 3: Cross multiply
   1,388.27x = 1,915.65 × 790.55
4. Step 4: Simplify right side
   1,388.27x = 1,514,417.11
5. Step 5: Solve for x
   x = 1,514,417.11/1,388.27
6. Step 6: Final answer
   x = 1,090.87