Finding the Third Proportional to 117,978 and 256,690

Step by Step Solution

1. Step 1: Write the proportion equation
   117,978 : 256,690 = 256,690 : x
2. Step 2: Convert to fraction form
   117,978/256,690 = 256,690/x
3. Step 3: Cross multiply
   117,978x = 256,690 × 256,690
4. Step 4: Simplify right side
   117,978x = 65,889,756,100
5. Step 5: Solve for x
   x = 65,889,756,100/117,978
6. Step 6: Final answer
   x = 558,491.89