Finding the Fourth Proportional to 89.72, 123.81 and 56.99

Step by Step Solution

1. Step 1: Write the proportion equation
   89.72 : 123.81 = 56.99 : x
2. Step 2: Convert to fraction form
   89.72/123.81 = 56.99/x
3. Step 3: Cross multiply
   89.72x = 123.81 × 56.99
4. Step 4: Simplify right side
   89.72x = 7,055.93
5. Step 5: Solve for x
   x = 7,055.93/89.72
6. Step 6: Final answer
   x = 78.64