Finding the Fourth Proportional to 91.58, 137.21 and 42.80

Step by Step Solution

1. Step 1: Write the proportion equation
   91.58 : 137.21 = 42.80 : x
2. Step 2: Convert to fraction form
   91.58/137.21 = 42.80/x
3. Step 3: Cross multiply
   91.58x = 137.21 × 42.80
4. Step 4: Simplify right side
   91.58x = 5,871.69
5. Step 5: Solve for x
   x = 5,871.69/91.58
6. Step 6: Final answer
   x = 64.12