Finding the Fourth Proportional to 1,015.02, 1,401.39 and 642.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,015.02 : 1,401.39 = 642.15 : x
2. Step 2: Convert to fraction form
   1,015.02/1,401.39 = 642.15/x
3. Step 3: Cross multiply
   1,015.02x = 1,401.39 × 642.15
4. Step 4: Simplify right side
   1,015.02x = 899,902.59
5. Step 5: Solve for x
   x = 899,902.59/1,015.02
6. Step 6: Final answer
   x = 886.59