Finding the Fourth Proportional to 2,978.78, 4,109.90 and 1,931.90

Step by Step Solution

1. Step 1: Write the proportion equation
   2,978.78 : 4,109.90 = 1,931.90 : x
2. Step 2: Convert to fraction form
   2,978.78/4,109.90 = 1,931.90/x
3. Step 3: Cross multiply
   2,978.78x = 4,109.90 × 1,931.90
4. Step 4: Simplify right side
   2,978.78x = 7,939,915.81
5. Step 5: Solve for x
   x = 7,939,915.81/2,978.78
6. Step 6: Final answer
   x = 2,665.49