Finding the Third Proportional to 39,720 and 55,890

Step by Step Solution

1. Step 1: Write the proportion equation
   39,720 : 55,890 = 55,890 : x
2. Step 2: Convert to fraction form
   39,720/55,890 = 55,890/x
3. Step 3: Cross multiply
   39,720x = 55,890 × 55,890
4. Step 4: Simplify right side
   39,720x = 3,123,692,100
5. Step 5: Solve for x
   x = 3,123,692,100/39,720
6. Step 6: Final answer
   x = 78,642.80