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Number of arrangements of the letters abcd in which neither ab nor cd come together.

Number of arrangements of the letters abcd in which neither ab nor cd come together.

Grade:11

2 Answers

Harsh Patodia IIT Roorkee
askIITians Faculty 907 Points
4 years ago
Take AB as one unit and CD as one unit.
These can be arranged 2! factorial ways. Internally each can be arranged in 2!
Total ways 2x2x2=8 -(1)
Now count AB as once unit. Total ways of arranging is . 3!2 =12 -(2)
Similary count CD as one unit. Total ways of arranging is 3!x2=12 -(3)
Total ways for AB or CD together= 2+3- =16
Total ways for AB or CD not together = 4!-16=8
SMILE FREE FIRE
26 Points
11 months ago
Tangents PA and PB are drawn to the circle x2 + y2 = 4, then the locus of the point P if the triangle PAB is equilatera
 

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