Finding the Third Proportional to 661.50 and 990.42

Step by Step Solution

1. Step 1: Write the proportion equation
   661.50 : 990.42 = 990.42 : x
2. Step 2: Convert to fraction form
   661.50/990.42 = 990.42/x
3. Step 3: Cross multiply
   661.50x = 990.42 × 990.42
4. Step 4: Simplify right side
   661.50x = 980,935.49
5. Step 5: Solve for x
   x = 980,935.49/661.50
6. Step 6: Final answer
   x = 1,482.90