Finding the Fourth Proportional to 2,148.78, 3,219.90 and 978.12

Step by Step Solution

1. Step 1: Write the proportion equation
   2,148.78 : 3,219.90 = 978.12 : x
2. Step 2: Convert to fraction form
   2,148.78/3,219.90 = 978.12/x
3. Step 3: Cross multiply
   2,148.78x = 3,219.90 × 978.12
4. Step 4: Simplify right side
   2,148.78x = 3,149,448.59
5. Step 5: Solve for x
   x = 3,149,448.59/2,148.78
6. Step 6: Final answer
   x = 1,465.69