Finding the Fourth Proportional to 1,388.91, 2,080.98 and 920.09

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.91 : 2,080.98 = 920.09 : x
2. Step 2: Convert to fraction form
   1,388.91/2,080.98 = 920.09/x
3. Step 3: Cross multiply
   1,388.91x = 2,080.98 × 920.09
4. Step 4: Simplify right side
   1,388.91x = 1,914,689.49
5. Step 5: Solve for x
   x = 1,914,689.49/1,388.91
6. Step 6: Final answer
   x = 1,378.55