Finding the Fourth Proportional to 1,335.56, 2,002.78 and 642.06

Step by Step Solution

1. Step 1: Write the proportion equation
   1,335.56 : 2,002.78 = 642.06 : x
2. Step 2: Convert to fraction form
   1,335.56/2,002.78 = 642.06/x
3. Step 3: Cross multiply
   1,335.56x = 2,002.78 × 642.06
4. Step 4: Simplify right side
   1,335.56x = 1,285,901.72
5. Step 5: Solve for x
   x = 1,285,901.72/1,335.56
6. Step 6: Final answer
   x = 962.82