Finding the Fourth Proportional to 12,786.21, 17,667.85 and 9,960.88

Step by Step Solution

1. Step 1: Write the proportion equation
   12,786.21 : 17,667.85 = 9,960.88 : x
2. Step 2: Convert to fraction form
   12,786.21/17,667.85 = 9,960.88/x
3. Step 3: Cross multiply
   12,786.21x = 17,667.85 × 9,960.88
4. Step 4: Simplify right side
   12,786.21x = 175,987,333.71
5. Step 5: Solve for x
   x = 175,987,333.71/12,786.21
6. Step 6: Final answer
   x = 13,763.84