7 4 2
7 4 6
7 4 1
7 4 6
Only at these placees 4 is preceded by 7 but not followed by 3
Given Number: 4 2 1 5 7 9 3 6 8
Ascending order: 1 2 3 4 5 6 7 8 9
Hence the required pairs are 12, 49, 16
Clearly, A?s new position is 15th from the left. But this is the same as B?s earlier position which is 9th from the right.
Number students behind the nitin in rank = (49 - 18) = 31
Nitin is 32nd from the last
Number of students in class = (8 + 1 + 37) = 46
Number of boys in the class = (18 + 1 +18) = 37
Three persons A, B, C can be arranged in a queue in six different ways, ie ABC, CBA, BAC, CAB, BCA, ACB. But since there are only 3 persons ahead of C, so C should be in front of the queue. Thus, there are only two possible arrangements, ie CBA and CAB.
We may consider the two cases as under:
Case I:
Clearly, number of persons in the queue = (3+1+8+1+5+1+21=) 40
Case II:
Number of persons between A and C
= (8 - 6) = 2
Clearly number of persons in the queue = (3+1+2+1+21) = 28
Now, 28 < 40. So, 28 is the minimum number of persons in the queue.
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