Finding the Fourth Proportional to 1,420.80, 1,960.90 and 861.27

Step by Step Solution

1. Step 1: Write the proportion equation
   1,420.80 : 1,960.90 = 861.27 : x
2. Step 2: Convert to fraction form
   1,420.80/1,960.90 = 861.27/x
3. Step 3: Cross multiply
   1,420.80x = 1,960.90 × 861.27
4. Step 4: Simplify right side
   1,420.80x = 1,688,864.34
5. Step 5: Solve for x
   x = 1,688,864.34/1,420.80
6. Step 6: Final answer
   x = 1,188.67