Finding the Fourth Proportional to 1,920.78, 2,880.90 and 688.02

Step by Step Solution

1. Step 1: Write the proportion equation
   1,920.78 : 2,880.90 = 688.02 : x
2. Step 2: Convert to fraction form
   1,920.78/2,880.90 = 688.02/x
3. Step 3: Cross multiply
   1,920.78x = 2,880.90 × 688.02
4. Step 4: Simplify right side
   1,920.78x = 1,982,116.82
5. Step 5: Solve for x
   x = 1,982,116.82/1,920.78
6. Step 6: Final answer
   x = 1,031.93