Finding the Third Proportional to 642 and 1,185.50

Step by Step Solution

1. Step 1: Write the proportion equation
   642 : 1,185.50 = 1,185.50 : x
2. Step 2: Convert to fraction form
   642/1,185.50 = 1,185.50/x
3. Step 3: Cross multiply
   642x = 1,185.50 × 1,185.50
4. Step 4: Simplify right side
   642x = 1,405,410.25
5. Step 5: Solve for x
   x = 1,405,410.25/642
6. Step 6: Final answer
   x = 2,189.11