Home / 89.40-123.21-81.71

Finding the Fourth Proportional to 89.40, 123.21 and 81.71

Calculator

Solution

The fourth proportional to 89.40, 123.21 and 81.71 is: 112.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    89.40 : 123.21 = 81.71 : x
  2. Step 2: Convert to fraction form
    89.40/123.21 = 81.71/x
  3. Step 3: Cross multiply
    89.40x = 123.21 × 81.71
  4. Step 4: Simplify right side
    89.40x = 10,067.49
  5. Step 5: Solve for x
    x = 10,067.49/89.40
  6. Step 6: Final answer
    x = 112.61

Related Problems

Find fourth proportional to 44.70, 61.61 and 40.86
Half scale
Find fourth proportional to 178.80, 246.42 and 163.42
Double scale
Find fourth proportional to 90.40, 124.59 and 82.71
Similar ratio
Find fourth proportional to 134.10, 184.82 and 122.57
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.