Finding the Fourth Proportional to 21,931, 32,904.72 and 13,172.20

Step by Step Solution

1. Step 1: Write the proportion equation
   21,931 : 32,904.72 = 13,172.20 : x
2. Step 2: Convert to fraction form
   21,931/32,904.72 = 13,172.20/x
3. Step 3: Cross multiply
   21,931x = 32,904.72 × 13,172.20
4. Step 4: Simplify right side
   21,931x = 433,427,552.78
5. Step 5: Solve for x
   x = 433,427,552.78/21,931
6. Step 6: Final answer
   x = 19,763.24