Finding the Fourth Proportional to 1,391.68, 1,921.62 and 861.34

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.68 : 1,921.62 = 861.34 : x
2. Step 2: Convert to fraction form
   1,391.68/1,921.62 = 861.34/x
3. Step 3: Cross multiply
   1,391.68x = 1,921.62 × 861.34
4. Step 4: Simplify right side
   1,391.68x = 1,655,168.17
5. Step 5: Solve for x
   x = 1,655,168.17/1,391.68
6. Step 6: Final answer
   x = 1,189.33