Finding the Third Proportional to 311,608.50 and 688,611

Step by Step Solution

1. Step 1: Write the proportion equation
   311,608.50 : 688,611 = 688,611 : x
2. Step 2: Convert to fraction form
   311,608.50/688,611 = 688,611/x
3. Step 3: Cross multiply
   311,608.50x = 688,611 × 688,611
4. Step 4: Simplify right side
   311,608.50x = 474,185,109,321
5. Step 5: Solve for x
   x = 474,185,109,321/311,608.50
6. Step 6: Final answer
   x = 1,521,733.55