Home / 83.78-115.31-61.91

Finding the Fourth Proportional to 83.78, 115.31 and 61.91

Calculator

Solution

The fourth proportional to 83.78, 115.31 and 61.91 is: 85.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    83.78 : 115.31 = 61.91 : x
  2. Step 2: Convert to fraction form
    83.78/115.31 = 61.91/x
  3. Step 3: Cross multiply
    83.78x = 115.31 × 61.91
  4. Step 4: Simplify right side
    83.78x = 7,138.42
  5. Step 5: Solve for x
    x = 7,138.42/83.78
  6. Step 6: Final answer
    x = 85.21

Related Problems

Find fourth proportional to 41.89, 57.66 and 30.95
Half scale
Find fourth proportional to 167.55, 230.63 and 123.81
Double scale
Find fourth proportional to 84.78, 116.69 and 62.91
Similar ratio
Find fourth proportional to 125.66, 172.97 and 92.86
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.