Home / 108.40-162.80-85.80

Finding the Fourth Proportional to 108.40, 162.80 and 85.80

Calculator

Solution

The fourth proportional to 108.40, 162.80 and 85.80 is: 128.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    108.40 : 162.80 = 85.80 : x
  2. Step 2: Convert to fraction form
    108.40/162.80 = 85.80/x
  3. Step 3: Cross multiply
    108.40x = 162.80 × 85.80
  4. Step 4: Simplify right side
    108.40x = 13,968.24
  5. Step 5: Solve for x
    x = 13,968.24/108.40
  6. Step 6: Final answer
    x = 128.86

Related Problems

Find fourth proportional to 54.20, 81.40 and 42.90
Half scale
Find fourth proportional to 216.80, 325.60 and 171.60
Double scale
Find fourth proportional to 109.40, 164.30 and 86.80
Similar ratio
Find fourth proportional to 162.60, 244.20 and 128.70
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.