Finding the Third Proportional to 686,300 and 990,072

Step by Step Solution

1. Step 1: Write the proportion equation
   686,300 : 990,072 = 990,072 : x
2. Step 2: Convert to fraction form
   686,300/990,072 = 990,072/x
3. Step 3: Cross multiply
   686,300x = 990,072 × 990,072
4. Step 4: Simplify right side
   686,300x = 980,242,565,184
5. Step 5: Solve for x
   x = 980,242,565,184/686,300
6. Step 6: Final answer
   x = 1,428,300.40