Finding the Fourth Proportional to 1,388.01, 2,080.81 and 521.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.01 : 2,080.81 = 521.72 : x
2. Step 2: Convert to fraction form
   1,388.01/2,080.81 = 521.72/x
3. Step 3: Cross multiply
   1,388.01x = 2,080.81 × 521.72
4. Step 4: Simplify right side
   1,388.01x = 1,085,595.31
5. Step 5: Solve for x
   x = 1,085,595.31/1,388.01
6. Step 6: Final answer
   x = 782.12