Finding the Fourth Proportional to 1,398.49, 1,926.57 and 978.05

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.49 : 1,926.57 = 978.05 : x
2. Step 2: Convert to fraction form
   1,398.49/1,926.57 = 978.05/x
3. Step 3: Cross multiply
   1,398.49x = 1,926.57 × 978.05
4. Step 4: Simplify right side
   1,398.49x = 1,884,281.79
5. Step 5: Solve for x
   x = 1,884,281.79/1,398.49
6. Step 6: Final answer
   x = 1,347.37