1
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
Total number of 6-digit numbers in which only and all the five digits 1, 3, 5, 7 and 9 appear, is :
A
$${5 \over 2}\left( {6!} \right)$$
B
$${6!}$$
C
56
D
$${1 \over 2}\left( {6!} \right)$$
2
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
A group of students comprises of 5 boys and n girls. If the number of ways, in which a team of 3 students can randomly be selected from this group such that there is at least one boy and at least one girl in each team, is 1750, then n is equal to :
A
24
B
25
C
27
D
28
3
JEE Main 2019 (Online) 12th April Morning Slot
+4
-1
The number of ways of choosing 10 objects out of 31 objects of which 10 are identical and the remaining 21 are distinct, is :
A
220 - 1
B
220
C
220 + 1
D
221
4
JEE Main 2019 (Online) 10th April Evening Slot
+4
-1
Suppose that 20 pillars of the same height have been erected along the boundary of a circular stadium. If the top of each pillar has been connected by beams with the top of all its non-adjacent pillars, then the total number of beams is :
A
180
B
210
C
170
D
190
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