If all the numbers from 5 to 85 which are exactly divisible by 5 are arranged in descending order, then which of the below given numbers shall come at the eleventh place from the bottom?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 55
In descending order the largest number comes first, so the bottom of the list holds the smallest numbers. Counting from the bottom is therefore counting up from 5.
The numbers are 5, 10, 15, …, 85, that is \(5\times1\) up to \(5\times17\): 17 numbers
From the bottom: 1st is 5, 2nd is 10, and the \(n\)th is \(5\times n\)
11th from the bottom \(=5\times11=55\)
Tip: In a descending list, the 11th from the bottom is also the \((17-11+1)=7\)th from the top: 85, 80, 75, 70, 65, 60, 55. Counting 11 from the top instead gives 35, which is Option (1).