Finding the Fourth Proportional to 1,015.41, 1,401.46 and 642.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,015.41 : 1,401.46 = 642.20 : x
2. Step 2: Convert to fraction form
   1,015.41/1,401.46 = 642.20/x
3. Step 3: Cross multiply
   1,015.41x = 1,401.46 × 642.20
4. Step 4: Simplify right side
   1,015.41x = 900,017.61
5. Step 5: Solve for x
   x = 900,017.61/1,015.41
6. Step 6: Final answer
   x = 886.36