Finding the Fourth Proportional to 1,399.98, 2,100.42 and 426.09

Step by Step Solution

1. Step 1: Write the proportion equation
   1,399.98 : 2,100.42 = 426.09 : x
2. Step 2: Convert to fraction form
   1,399.98/2,100.42 = 426.09/x
3. Step 3: Cross multiply
   1,399.98x = 2,100.42 × 426.09
4. Step 4: Simplify right side
   1,399.98x = 894,967.96
5. Step 5: Solve for x
   x = 894,967.96/1,399.98
6. Step 6: Final answer
   x = 639.27