Finding the Fourth Proportional to 1,420.88, 1,960.31 and 861.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,420.88 : 1,960.31 = 861.12 : x
2. Step 2: Convert to fraction form
   1,420.88/1,960.31 = 861.12/x
3. Step 3: Cross multiply
   1,420.88x = 1,960.31 × 861.12
4. Step 4: Simplify right side
   1,420.88x = 1,688,064.30
5. Step 5: Solve for x
   x = 1,688,064.30/1,420.88
6. Step 6: Final answer
   x = 1,188.05