Home / 38.80-58.18-20.78

Finding the Fourth Proportional to 38.80, 58.18 and 20.78

Calculator

Solution

The fourth proportional to 38.80, 58.18 and 20.78 is: 31.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    38.80 : 58.18 = 20.78 : x
  2. Step 2: Convert to fraction form
    38.80/58.18 = 20.78/x
  3. Step 3: Cross multiply
    38.80x = 58.18 × 20.78
  4. Step 4: Simplify right side
    38.80x = 1,208.98
  5. Step 5: Solve for x
    x = 1,208.98/38.80
  6. Step 6: Final answer
    x = 31.16

Related Problems

Find fourth proportional to 19.40, 29.09 and 10.39
Half scale
Find fourth proportional to 77.60, 116.36 and 41.56
Double scale
Find fourth proportional to 39.80, 59.68 and 21.78
Similar ratio
Find fourth proportional to 58.20, 87.27 and 31.17
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.