Question-51286

Question Number 51286 by aseerimad last updated on 25/Dec/18

Answered by mr W last updated on 26/Dec/18

T y p e 1 :

N u m b e r o f w o r d s s t a r t i n g w i t h D :

= \frac{7!}{2!} = 2520

T y p e 2 :

N u m b e r o f w o r d s e n d i n g w i t h R :

= \frac{2! 7!}{2!} = 5040

b u t i n t h i s n u m b e r s o m e w o r d s s t a r t

w i t h D w h i c h a r e a l r e a d y c o u n t e d i n

t y p e 1 .

T y p e 3 :

N u m b e r o f w o r d s e n d i n g w i t h R b u t

s t a r t i n g w i t h D :

= \frac{2! 6!}{2!} = 720

\Rightarrow r e s u l t i s 2520 + 5040 - 720 = 6840

Commented by Tawa1 last updated on 26/Dec/18

God bless you sir, i learn more

Commented by aseerimad last updated on 26/Dec/18

t h a n k y o u s i r .