Finding the Third Proportional to 638.63 and 1,290.56

Step by Step Solution

1. Step 1: Write the proportion equation
   638.63 : 1,290.56 = 1,290.56 : x
2. Step 2: Convert to fraction form
   638.63/1,290.56 = 1,290.56/x
3. Step 3: Cross multiply
   638.63x = 1,290.56 × 1,290.56
4. Step 4: Simplify right side
   638.63x = 1,665,551.57
5. Step 5: Solve for x
   x = 1,665,551.57/638.63
6. Step 6: Final answer
   x = 2,608.03