Home / 66.78-91.20-63.90

Finding the Fourth Proportional to 66.78, 91.20 and 63.90

Calculator

Solution

The fourth proportional to 66.78, 91.20 and 63.90 is: 87.27

Step by Step Solution

  1. Step 1: Write the proportion equation
    66.78 : 91.20 = 63.90 : x
  2. Step 2: Convert to fraction form
    66.78/91.20 = 63.90/x
  3. Step 3: Cross multiply
    66.78x = 91.20 × 63.90
  4. Step 4: Simplify right side
    66.78x = 5,827.68
  5. Step 5: Solve for x
    x = 5,827.68/66.78
  6. Step 6: Final answer
    x = 87.27

Related Problems

Find fourth proportional to 33.39, 45.60 and 31.95
Half scale
Find fourth proportional to 133.56, 182.40 and 127.80
Double scale
Find fourth proportional to 67.78, 92.57 and 64.90
Similar ratio
Find fourth proportional to 100.17, 136.80 and 95.85
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.