Finding the Fourth Proportional to 12,690.56, 17,510.90 and 7,971.50

Step by Step Solution

1. Step 1: Write the proportion equation
   12,690.56 : 17,510.90 = 7,971.50 : x
2. Step 2: Convert to fraction form
   12,690.56/17,510.90 = 7,971.50/x
3. Step 3: Cross multiply
   12,690.56x = 17,510.90 × 7,971.50
4. Step 4: Simplify right side
   12,690.56x = 139,588,011.94
5. Step 5: Solve for x
   x = 139,588,011.94/12,690.56
6. Step 6: Final answer
   x = 10,999.36