Question

How many 5’s are there in the given sequence which are immediately followed by 3, not immediately preceded by 7?
8953253855687335775365335798
(a) Two
(b) One
(c) Four
(d) Three

Answer 1

Hint: We start solving the problem by underlining the 5’s in the sequence which were immediately followed by 3 (3 should be just after 5) in the given sequence. We then cross the underlined 5’s that were immediately preceded by 7 (7 should be just before 5). We then count the number of 5’s that were underlined but not crossed in the sequence to get the required answer.

Complete step-by-step answer:
According to the problem, we are given a sequence 8953253855687335775365335798 and we need to find the number of 5’s in this sequence which were immediately followed by 3, but not immediately preceded by 7.
Now, let us underline the 5’s that were immediately followed by 3 (3 should be just after 5) in the given sequence as shown below:
8953253855687335775365335798.
Now, let us cross the underlined 5’s which were immediately preceded by 7 (5 should be just before 5) in the given sequence as shown below:
8953253855687335775365335798.
No, we can see that there are a total of three 5’s present in the given sequence satisfying the given conditions.
So, the total number of 5’s in this sequence which were immediately followed by 3, but not immediately preceded by 7 is three.
∴ The correct option for the given problem is (d).

So, the correct answer is “Option (d)”.

Note: We should not confuse with preceding and following the numbers while solving the numbers. Whenever we get this type of problem, we try to solve it by marking the required numbers first as this will reduce confusion while solving the problem. Similarly, we can expect problems to find the total number of 5’s that were immediately preceded by 3 and immediately followed by 7.