Which of the following is the lowest ratio?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 7 : 15
A ratio a : b is the fraction a/b, so the ratios can be compared by their decimal values:
15 : 23 \(=0.652\)
21 : 39 \(=0.538\)
7 : 15 \(=0.467\)
17 : 25 \(=0.68\)
The smallest value is 0.467, so the lowest ratio is 7 : 15.
Shortcut:
7 : 15 is the only ratio less than one-half (7 is less than half of 15)
15 : 23, 21 : 39 and 17 : 25 each have a first term more than half the second, so 7 : 15 is the lowest