Finding the Fourth Proportional to 1,290.89, 1,936.34 and 425.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,290.89 : 1,936.34 = 425.21 : x
2. Step 2: Convert to fraction form
   1,290.89/1,936.34 = 425.21/x
3. Step 3: Cross multiply
   1,290.89x = 1,936.34 × 425.21
4. Step 4: Simplify right side
   1,290.89x = 823,339.32
5. Step 5: Solve for x
   x = 823,339.32/1,290.89
6. Step 6: Final answer
   x = 637.81