Finding the Fourth Proportional to 11,739.72, 17,621.16 and 7,980

Step by Step Solution

1. Step 1: Write the proportion equation
   11,739.72 : 17,621.16 = 7,980 : x
2. Step 2: Convert to fraction form
   11,739.72/17,621.16 = 7,980/x
3. Step 3: Cross multiply
   11,739.72x = 17,621.16 × 7,980
4. Step 4: Simplify right side
   11,739.72x = 140,616,856.80
5. Step 5: Solve for x
   x = 140,616,856.80/11,739.72
6. Step 6: Final answer
   x = 11,977.87