Home / 91.30-136.80-85.90

Finding the Fourth Proportional to 91.30, 136.80 and 85.90

Calculator

Solution

The fourth proportional to 91.30, 136.80 and 85.90 is: 128.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.30 : 136.80 = 85.90 : x
  2. Step 2: Convert to fraction form
    91.30/136.80 = 85.90/x
  3. Step 3: Cross multiply
    91.30x = 136.80 × 85.90
  4. Step 4: Simplify right side
    91.30x = 11,751.12
  5. Step 5: Solve for x
    x = 11,751.12/91.30
  6. Step 6: Final answer
    x = 128.71

Related Problems

Find fourth proportional to 45.65, 68.40 and 42.95
Half scale
Find fourth proportional to 182.60, 273.60 and 171.80
Double scale
Find fourth proportional to 92.30, 138.30 and 86.90
Similar ratio
Find fourth proportional to 136.95, 205.20 and 128.85
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.