Finding the Fourth Proportional to 1,686.35, 2,326.78 and 978.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,686.35 : 2,326.78 = 978.31 : x
2. Step 2: Convert to fraction form
   1,686.35/2,326.78 = 978.31/x
3. Step 3: Cross multiply
   1,686.35x = 2,326.78 × 978.31
4. Step 4: Simplify right side
   1,686.35x = 2,276,312.14
5. Step 5: Solve for x
   x = 2,276,312.14/1,686.35
6. Step 6: Final answer
   x = 1,349.85