Finding the Third Proportional to 647.58 and 990.56

Step by Step Solution

1. Step 1: Write the proportion equation
   647.58 : 990.56 = 990.56 : x
2. Step 2: Convert to fraction form
   647.58/990.56 = 990.56/x
3. Step 3: Cross multiply
   647.58x = 990.56 × 990.56
4. Step 4: Simplify right side
   647.58x = 981,214.07
5. Step 5: Solve for x
   x = 981,214.07/647.58
6. Step 6: Final answer
   x = 1,515.21