Finding the Fourth Proportional to 1,015.88, 1,401.72 and 642.92

Step by Step Solution

1. Step 1: Write the proportion equation
   1,015.88 : 1,401.72 = 642.92 : x
2. Step 2: Convert to fraction form
   1,015.88/1,401.72 = 642.92/x
3. Step 3: Cross multiply
   1,015.88x = 1,401.72 × 642.92
4. Step 4: Simplify right side
   1,015.88x = 901,193.82
5. Step 5: Solve for x
   x = 901,193.82/1,015.88
6. Step 6: Final answer
   x = 887.11