Finding the Fourth Proportional to 89.39, 123.18 and 64.78

Step by Step Solution

1. Step 1: Write the proportion equation
   89.39 : 123.18 = 64.78 : x
2. Step 2: Convert to fraction form
   89.39/123.18 = 64.78/x
3. Step 3: Cross multiply
   89.39x = 123.18 × 64.78
4. Step 4: Simplify right side
   89.39x = 7,979.29
5. Step 5: Solve for x
   x = 7,979.29/89.39
6. Step 6: Final answer
   x = 89.27