Finding the Third Proportional to 978.19 and 1,243.69

Step by Step Solution

1. Step 1: Write the proportion equation
   978.19 : 1,243.69 = 1,243.69 : x
2. Step 2: Convert to fraction form
   978.19/1,243.69 = 1,243.69/x
3. Step 3: Cross multiply
   978.19x = 1,243.69 × 1,243.69
4. Step 4: Simplify right side
   978.19x = 1,546,758.60
5. Step 5: Solve for x
   x = 1,546,758.60/978.19
6. Step 6: Final answer
   x = 1,581.25