Finding the Fourth Proportional to 56.91, 78.54 and 42.18

Step by Step Solution

1. Step 1: Write the proportion equation
   56.91 : 78.54 = 42.18 : x
2. Step 2: Convert to fraction form
   56.91/78.54 = 42.18/x
3. Step 3: Cross multiply
   56.91x = 78.54 × 42.18
4. Step 4: Simplify right side
   56.91x = 3,312.82
5. Step 5: Solve for x
   x = 3,312.82/56.91
6. Step 6: Final answer
   x = 58.21