Home / 390.80-539.53-311.87

Finding the Fourth Proportional to 390.80, 539.53 and 311.87

Calculator

Solution

The fourth proportional to 390.80, 539.53 and 311.87 is: 430.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.80 : 539.53 = 311.87 : x
  2. Step 2: Convert to fraction form
    390.80/539.53 = 311.87/x
  3. Step 3: Cross multiply
    390.80x = 539.53 × 311.87
  4. Step 4: Simplify right side
    390.80x = 168,258.96
  5. Step 5: Solve for x
    x = 168,258.96/390.80
  6. Step 6: Final answer
    x = 430.55

Related Problems

Find fourth proportional to 195.40, 269.76 and 155.93
Half scale
Find fourth proportional to 781.60, 1,079.05 and 623.73
Double scale
Find fourth proportional to 391.80, 540.91 and 312.87
Similar ratio
Find fourth proportional to 586.20, 809.29 and 467.80
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.