Home / 485.80-728.70-139.10

Finding the Fourth Proportional to 485.80, 728.70 and 139.10

Calculator

Solution

The fourth proportional to 485.80, 728.70 and 139.10 is: 208.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    485.80 : 728.70 = 139.10 : x
  2. Step 2: Convert to fraction form
    485.80/728.70 = 139.10/x
  3. Step 3: Cross multiply
    485.80x = 728.70 × 139.10
  4. Step 4: Simplify right side
    485.80x = 101,362.17
  5. Step 5: Solve for x
    x = 101,362.17/485.80
  6. Step 6: Final answer
    x = 208.65

Related Problems

Find fourth proportional to 242.90, 364.35 and 69.55
Half scale
Find fourth proportional to 971.60, 1,457.40 and 278.20
Double scale
Find fourth proportional to 486.80, 730.20 and 140.10
Similar ratio
Find fourth proportional to 728.70, 1,093.05 and 208.65
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.