Finding the Third Proportional to 400,408 and 870,040

Step by Step Solution

1. Step 1: Write the proportion equation
   400,408 : 870,040 = 870,040 : x
2. Step 2: Convert to fraction form
   400,408/870,040 = 870,040/x
3. Step 3: Cross multiply
   400,408x = 870,040 × 870,040
4. Step 4: Simplify right side
   400,408x = 756,969,601,600
5. Step 5: Solve for x
   x = 756,969,601,600/400,408
6. Step 6: Final answer
   x = 1,890,495.70