Finding the Fourth Proportional to 2,640.76, 3,953.84 and 1,989.52

Step by Step Solution

1. Step 1: Write the proportion equation
   2,640.76 : 3,953.84 = 1,989.52 : x
2. Step 2: Convert to fraction form
   2,640.76/3,953.84 = 1,989.52/x
3. Step 3: Cross multiply
   2,640.76x = 3,953.84 × 1,989.52
4. Step 4: Simplify right side
   2,640.76x = 7,866,243.76
5. Step 5: Solve for x
   x = 7,866,243.76/2,640.76
6. Step 6: Final answer
   x = 2,978.78