Home / 31.40-47.20-30.78

Finding the Fourth Proportional to 31.40, 47.20 and 30.78

Calculator

Solution

The fourth proportional to 31.40, 47.20 and 30.78 is: 46.27

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.40 : 47.20 = 30.78 : x
  2. Step 2: Convert to fraction form
    31.40/47.20 = 30.78/x
  3. Step 3: Cross multiply
    31.40x = 47.20 × 30.78
  4. Step 4: Simplify right side
    31.40x = 1,452.82
  5. Step 5: Solve for x
    x = 1,452.82/31.40
  6. Step 6: Final answer
    x = 46.27

Related Problems

Find fourth proportional to 15.70, 23.60 and 15.39
Half scale
Find fourth proportional to 62.80, 94.40 and 61.56
Double scale
Find fourth proportional to 32.40, 48.70 and 31.78
Similar ratio
Find fourth proportional to 47.10, 70.80 and 46.17
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.