Finding the Third Proportional to 261,278 and 390,900

Step by Step Solution

1. Step 1: Write the proportion equation
   261,278 : 390,900 = 390,900 : x
2. Step 2: Convert to fraction form
   261,278/390,900 = 390,900/x
3. Step 3: Cross multiply
   261,278x = 390,900 × 390,900
4. Step 4: Simplify right side
   261,278x = 152,802,810,000
5. Step 5: Solve for x
   x = 152,802,810,000/261,278
6. Step 6: Final answer
   x = 584,828.46