Finding the Third Proportional to 261,258 and 390,870

Step by Step Solution

1. Step 1: Write the proportion equation
   261,258 : 390,870 = 390,870 : x
2. Step 2: Convert to fraction form
   261,258/390,870 = 390,870/x
3. Step 3: Cross multiply
   261,258x = 390,870 × 390,870
4. Step 4: Simplify right side
   261,258x = 152,779,356,900
5. Step 5: Solve for x
   x = 152,779,356,900/261,258
6. Step 6: Final answer
   x = 584,783.46