Finding the Fourth Proportional to 1,009.21, 1,392.34 and 636.05

Step by Step Solution

1. Step 1: Write the proportion equation
   1,009.21 : 1,392.34 = 636.05 : x
2. Step 2: Convert to fraction form
   1,009.21/1,392.34 = 636.05/x
3. Step 3: Cross multiply
   1,009.21x = 1,392.34 × 636.05
4. Step 4: Simplify right side
   1,009.21x = 885,587.72
5. Step 5: Solve for x
   x = 885,587.72/1,009.21
6. Step 6: Final answer
   x = 877.51