Home / 840.96-1,256.60-642.20

Finding the Fourth Proportional to 840.96, 1,256.60 and 642.20

Calculator

Solution

The fourth proportional to 840.96, 1,256.60 and 642.20 is: 959.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    840.96 : 1,256.60 = 642.20 : x
  2. Step 2: Convert to fraction form
    840.96/1,256.60 = 642.20/x
  3. Step 3: Cross multiply
    840.96x = 1,256.60 × 642.20
  4. Step 4: Simplify right side
    840.96x = 806,983.84
  5. Step 5: Solve for x
    x = 806,983.84/840.96
  6. Step 6: Final answer
    x = 959.60

Related Problems

Find fourth proportional to 420.48, 628.30 and 321.10
Half scale
Find fourth proportional to 1,681.92, 2,513.21 and 1,284.39
Double scale
Find fourth proportional to 841.96, 1,258.10 and 643.20
Similar ratio
Find fourth proportional to 1,261.44, 1,884.90 and 963.29
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.