Finding the Fourth Proportional to 1,421.12, 1,959.71 and 861.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,421.12 : 1,959.71 = 861.50 : x
2. Step 2: Convert to fraction form
   1,421.12/1,959.71 = 861.50/x
3. Step 3: Cross multiply
   1,421.12x = 1,959.71 × 861.50
4. Step 4: Simplify right side
   1,421.12x = 1,688,276.06
5. Step 5: Solve for x
   x = 1,688,276.06/1,421.12
6. Step 6: Final answer
   x = 1,187.99