Finding the Fourth Proportional to 1,187.34, 1,638.81 and 721.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,187.34 : 1,638.81 = 721.50 : x
2. Step 2: Convert to fraction form
   1,187.34/1,638.81 = 721.50/x
3. Step 3: Cross multiply
   1,187.34x = 1,638.81 × 721.50
4. Step 4: Simplify right side
   1,187.34x = 1,182,401.42
5. Step 5: Solve for x
   x = 1,182,401.42/1,187.34
6. Step 6: Final answer
   x = 995.84