Home / 90.72-135.14-87.21

Finding the Fourth Proportional to 90.72, 135.14 and 87.21

Calculator

Solution

The fourth proportional to 90.72, 135.14 and 87.21 is: 129.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.72 : 135.14 = 87.21 : x
  2. Step 2: Convert to fraction form
    90.72/135.14 = 87.21/x
  3. Step 3: Cross multiply
    90.72x = 135.14 × 87.21
  4. Step 4: Simplify right side
    90.72x = 11,785.12
  5. Step 5: Solve for x
    x = 11,785.12/90.72
  6. Step 6: Final answer
    x = 129.91

Related Problems

Find fourth proportional to 45.36, 67.57 and 43.61
Half scale
Find fourth proportional to 181.44, 270.27 and 174.42
Double scale
Find fourth proportional to 91.72, 136.62 and 88.21
Similar ratio
Find fourth proportional to 136.08, 202.70 and 130.82
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.