Finding the Fourth Proportional to 2,620.37, 3,929.78 and 770.90

Step by Step Solution

1. Step 1: Write the proportion equation
   2,620.37 : 3,929.78 = 770.90 : x
2. Step 2: Convert to fraction form
   2,620.37/3,929.78 = 770.90/x
3. Step 3: Cross multiply
   2,620.37x = 3,929.78 × 770.90
4. Step 4: Simplify right side
   2,620.37x = 3,029,443.90
5. Step 5: Solve for x
   x = 3,029,443.90/2,620.37
6. Step 6: Final answer
   x = 1,156.12