Finding the Fourth Proportional to 5,091.78, 7,640.53 and 3,978.07

Step by Step Solution

1. Step 1: Write the proportion equation
   5,091.78 : 7,640.53 = 3,978.07 : x
2. Step 2: Convert to fraction form
   5,091.78/7,640.53 = 3,978.07/x
3. Step 3: Cross multiply
   5,091.78x = 7,640.53 × 3,978.07
4. Step 4: Simplify right side
   5,091.78x = 30,394,563.18
5. Step 5: Solve for x
   x = 30,394,563.18/5,091.78
6. Step 6: Final answer
   x = 5,969.34