Finding the Fourth Proportional to 1,231.29, 1,699.84 and 978.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,231.29 : 1,699.84 = 978.72 : x
2. Step 2: Convert to fraction form
   1,231.29/1,699.84 = 978.72/x
3. Step 3: Cross multiply
   1,231.29x = 1,699.84 × 978.72
4. Step 4: Simplify right side
   1,231.29x = 1,663,662.25
5. Step 5: Solve for x
   x = 1,663,662.25/1,231.29
6. Step 6: Final answer
   x = 1,351.15