Finding the Third Proportional to 691 and 1,621.38

Step by Step Solution

1. Step 1: Write the proportion equation
   691 : 1,621.38 = 1,621.38 : x
2. Step 2: Convert to fraction form
   691/1,621.38 = 1,621.38/x
3. Step 3: Cross multiply
   691x = 1,621.38 × 1,621.38
4. Step 4: Simplify right side
   691x = 2,628,856.89
5. Step 5: Solve for x
   x = 2,628,856.89/691
6. Step 6: Final answer
   x = 3,804.42