Finding the Fourth Proportional to 20,412, 28,170.72 and 12,960

Step by Step Solution

1. Step 1: Write the proportion equation
   20,412 : 28,170.72 = 12,960 : x
2. Step 2: Convert to fraction form
   20,412/28,170.72 = 12,960/x
3. Step 3: Cross multiply
   20,412x = 28,170.72 × 12,960
4. Step 4: Simplify right side
   20,412x = 365,092,531.20
5. Step 5: Solve for x
   x = 365,092,531.20/20,412
6. Step 6: Final answer
   x = 17,886.17