Finding the Fourth Proportional to 1,238.31, 1,858.92 and 978.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,238.31 : 1,858.92 = 978.50 : x
2. Step 2: Convert to fraction form
   1,238.31/1,858.92 = 978.50/x
3. Step 3: Cross multiply
   1,238.31x = 1,858.92 × 978.50
4. Step 4: Simplify right side
   1,238.31x = 1,818,954.20
5. Step 5: Solve for x
   x = 1,818,954.20/1,238.31
6. Step 6: Final answer
   x = 1,468.90