Finding the Fourth Proportional to 85.90, 128.75 and 42.00

Step by Step Solution

1. Step 1: Write the proportion equation
   85.90 : 128.75 = 42.00 : x
2. Step 2: Convert to fraction form
   85.90/128.75 = 42.00/x
3. Step 3: Cross multiply
   85.90x = 128.75 × 42.00
4. Step 4: Simplify right side
   85.90x = 5,407.15
5. Step 5: Solve for x
   x = 5,407.15/85.90
6. Step 6: Final answer
   x = 62.95