Home / 390.80-539.30-216.15

Finding the Fourth Proportional to 390.80, 539.30 and 216.15

Calculator

Solution

The fourth proportional to 390.80, 539.30 and 216.15 is: 298.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.80 : 539.30 = 216.15 : x
  2. Step 2: Convert to fraction form
    390.80/539.30 = 216.15/x
  3. Step 3: Cross multiply
    390.80x = 539.30 × 216.15
  4. Step 4: Simplify right side
    390.80x = 116,568.21
  5. Step 5: Solve for x
    x = 116,568.21/390.80
  6. Step 6: Final answer
    x = 298.28

Related Problems

Find fourth proportional to 195.40, 269.65 and 108.07
Half scale
Find fourth proportional to 781.61, 1,078.61 and 432.29
Double scale
Find fourth proportional to 391.80, 540.68 and 217.15
Similar ratio
Find fourth proportional to 586.20, 808.95 and 324.22
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.