Verified Solution • 2025–26 Session moderate

QJEEM25Mab2c1: JEE Main 2025 Mathematics - Class 11 JEEM25Mab2c1 Solution: In a group of 3 girls and 4 boys, there are two boys and . The…

In a group of 3 girls and 4 boys, there are two boys B1B_1 and B2B_2 . The number of ways, in which these girls and boys can stand in a queue such that all the girls stand together, all the boys stand together, but B1B_1 and B2B_2 are not adjacent to each other, is :

Multiple Choice Options

  • A 120
  • B 96
  • C 72
  • D 144

Step-by-Step Verified Solution

Let's break the problem down step by step:

There are two blocks because all girls must stand together and all boys must stand together. The two blocks can be arranged in:

2 ways(i.e., girls first then boys, or boys first then girls).

The girls can be arranged among themselves in:

3!=6 ways.

For the boys (4 in total), they must be arranged such that the specific boys B1B_1 and B2B_2 are not adjacent.

First, calculate the total number of arrangements of 4 boys:

4!=24.

Next, count the arrangements where B1B_1 and B2B_2 are adjacent. Think of B1B_1 and B2B_2 as a single unit. This unit can be arranged in:

2!=2 ways (since B1 and B2 can swap positions).

Now, with this new unit, we have 3 units in total (the B1B2B_1B_2 unit and the other 2 boys), which can be arranged in:

3!=6 ways.

So, the number of arrangements where B1B_1 and B2B_2 are adjacent is:

2!×3!=2×6=12.

Therefore, the number of valid arrangements for the boys where B1B_1 and B2B_2 are not adjacent is:

24−12=12.

Finally, multiply all the factors together:

Total ways=2×6×12=144.

Thus, the number of ways in which the girls and boys can stand in the queue under the given conditions is 144.

This corresponds to Option D.

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