Finding the Fourth Proportional to 1,421.23, 1,961.31 and 861.60

Step by Step Solution

1. Step 1: Write the proportion equation
   1,421.23 : 1,961.31 = 861.60 : x
2. Step 2: Convert to fraction form
   1,421.23/1,961.31 = 861.60/x
3. Step 3: Cross multiply
   1,421.23x = 1,961.31 × 861.60
4. Step 4: Simplify right side
   1,421.23x = 1,689,875.28
5. Step 5: Solve for x
   x = 1,689,875.28/1,421.23
6. Step 6: Final answer
   x = 1,189.02