UPSC NDA Math Model Paper 6

We can do the segregation of the toys as follows:
(Select 4 toys out of 10 toys) AND (Select 2 toys out of remaining 6 toys) AND (Select 2 toys out of remaining 4 toys) AND (Select 2 toys out of remaining 2 toys)
The required number of ways is, therefore:
=‌10C4×‌6C2×‌4C2×‌2C2
=

10!

4!(10−4)!

×

6!

2!(6−2)!

×

4!

2!(4−2)!

×

2!

2!(2−2)!

=210×15×6×1
=18900