Finding the Fourth Proportional to 1,421.28, 1,960.56 and 861.48

Step by Step Solution

1. Step 1: Write the proportion equation
   1,421.28 : 1,960.56 = 861.48 : x
2. Step 2: Convert to fraction form
   1,421.28/1,960.56 = 861.48/x
3. Step 3: Cross multiply
   1,421.28x = 1,960.56 × 861.48
4. Step 4: Simplify right side
   1,421.28x = 1,688,983.23
5. Step 5: Solve for x
   x = 1,688,983.23/1,421.28
6. Step 6: Final answer
   x = 1,188.35