Question

The ratio of tagged fish to untagged fish was 2 to 9. Ninety fish were tagged. How many fish were untagged

Answer 1

405

Explanation:

Since

2 : 9 = 90 : X

Then we know

9/2 = X/90

Multiplying both sides by 90 cancels on the right

90 × (9/2) = (X/90) × 90

90 × (9/2) = X

Then solving for X

X = 90 × (9/2)

X = 405

Therefore

2 : 9 = 90 : 405