Finding the Fourth Proportional to 72.96, 100.72 and 56.64

Step by Step Solution

1. Step 1: Write the proportion equation
   72.96 : 100.72 = 56.64 : x
2. Step 2: Convert to fraction form
   72.96/100.72 = 56.64/x
3. Step 3: Cross multiply
   72.96x = 100.72 × 56.64
4. Step 4: Simplify right side
   72.96x = 5,704.78
5. Step 5: Solve for x
   x = 5,704.78/72.96
6. Step 6: Final answer
   x = 78.19