Finding the Fourth Proportional to 1,288.71, 1,777.88 and 790.49

Step by Step Solution

1. Step 1: Write the proportion equation
   1,288.71 : 1,777.88 = 790.49 : x
2. Step 2: Convert to fraction form
   1,288.71/1,777.88 = 790.49/x
3. Step 3: Cross multiply
   1,288.71x = 1,777.88 × 790.49
4. Step 4: Simplify right side
   1,288.71x = 1,405,402.78
5. Step 5: Solve for x
   x = 1,405,402.78/1,288.71
6. Step 6: Final answer
   x = 1,090.55