Home / 77-115.50-20

Finding the Fourth Proportional to 77, 115.50 and 20

Calculator

Solution

The fourth proportional to 77, 115.50 and 20 is: 30

Step by Step Solution

  1. Step 1: Write the proportion equation
    77 : 115.50 = 20 : x
  2. Step 2: Convert to fraction form
    77/115.50 = 20/x
  3. Step 3: Cross multiply
    77x = 115.50 × 20
  4. Step 4: Simplify right side
    77x = 2,310
  5. Step 5: Solve for x
    x = 2,310/77
  6. Step 6: Final answer
    x = 30

Related Problems

Find fourth proportional to 38.50, 57.75 and 10
Half scale
Find fourth proportional to 154, 231 and 40
Double scale
Find fourth proportional to 78, 117 and 21
Similar ratio
Find fourth proportional to 115.50, 173.25 and 30
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.