Finding the Fourth Proportional to 21,091, 29,085.78 and 13,531.51

Step by Step Solution

1. Step 1: Write the proportion equation
   21,091 : 29,085.78 = 13,531.51 : x
2. Step 2: Convert to fraction form
   21,091/29,085.78 = 13,531.51/x
3. Step 3: Cross multiply
   21,091x = 29,085.78 × 13,531.51
4. Step 4: Simplify right side
   21,091x = 393,574,522.93
5. Step 5: Solve for x
   x = 393,574,522.93/21,091
6. Step 6: Final answer
   x = 18,660.78