Home / 80.15-120.20-28.78

Finding the Fourth Proportional to 80.15, 120.20 and 28.78

Calculator

Solution

The fourth proportional to 80.15, 120.20 and 28.78 is: 43.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    80.15 : 120.20 = 28.78 : x
  2. Step 2: Convert to fraction form
    80.15/120.20 = 28.78/x
  3. Step 3: Cross multiply
    80.15x = 120.20 × 28.78
  4. Step 4: Simplify right side
    80.15x = 3,458.61
  5. Step 5: Solve for x
    x = 3,458.61/80.15
  6. Step 6: Final answer
    x = 43.15

Related Problems

Find fourth proportional to 40.07, 60.10 and 14.39
Half scale
Find fourth proportional to 160.29, 240.39 and 57.55
Double scale
Find fourth proportional to 81.15, 121.69 and 29.78
Similar ratio
Find fourth proportional to 120.22, 180.29 and 43.16
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.