Finding the Third Proportional to 390,521 and 812,142

Step by Step Solution

1. Step 1: Write the proportion equation
   390,521 : 812,142 = 812,142 : x
2. Step 2: Convert to fraction form
   390,521/812,142 = 812,142/x
3. Step 3: Cross multiply
   390,521x = 812,142 × 812,142
4. Step 4: Simplify right side
   390,521x = 659,574,628,164
5. Step 5: Solve for x
   x = 659,574,628,164/390,521
6. Step 6: Final answer
   x = 1,688,960.72