Finding the Fourth Proportional to 1,015.72, 1,401.91 and 642.46

Step by Step Solution

1. Step 1: Write the proportion equation
   1,015.72 : 1,401.91 = 642.46 : x
2. Step 2: Convert to fraction form
   1,015.72/1,401.91 = 642.46/x
3. Step 3: Cross multiply
   1,015.72x = 1,401.91 × 642.46
4. Step 4: Simplify right side
   1,015.72x = 900,671.10
5. Step 5: Solve for x
   x = 900,671.10/1,015.72
6. Step 6: Final answer
   x = 886.73