Finding the Third Proportional to 3,980.81 and 8,690.63

Step by Step Solution

1. Step 1: Write the proportion equation
   3,980.81 : 8,690.63 = 8,690.63 : x
2. Step 2: Convert to fraction form
   3,980.81/8,690.63 = 8,690.63/x
3. Step 3: Cross multiply
   3,980.81x = 8,690.63 × 8,690.63
4. Step 4: Simplify right side
   3,980.81x = 75,526,962.89
5. Step 5: Solve for x
   x = 75,526,962.89/3,980.81
6. Step 6: Final answer
   x = 18,972.75