Finding the Third Proportional to 978 and 1,321.50

Step by Step Solution

1. Step 1: Write the proportion equation
   978 : 1,321.50 = 1,321.50 : x
2. Step 2: Convert to fraction form
   978/1,321.50 = 1,321.50/x
3. Step 3: Cross multiply
   978x = 1,321.50 × 1,321.50
4. Step 4: Simplify right side
   978x = 1,746,362.25
5. Step 5: Solve for x
   x = 1,746,362.25/978
6. Step 6: Final answer
   x = 1,785.65