Finding the Third Proportional to 7,920 and 12,487.50

Step by Step Solution

1. Step 1: Write the proportion equation
   7,920 : 12,487.50 = 12,487.50 : x
2. Step 2: Convert to fraction form
   7,920/12,487.50 = 12,487.50/x
3. Step 3: Cross multiply
   7,920x = 12,487.50 × 12,487.50
4. Step 4: Simplify right side
   7,920x = 155,937,656.25
5. Step 5: Solve for x
   x = 155,937,656.25/7,920
6. Step 6: Final answer
   x = 19,689.10