Question

In the Suniti Building in Mumbai there are 12 floors plus
the ground floor.9 people get into the lift of the building
on the ground floor.The lift does not stop on the first floor.
If 2,3 and 4 people alight from the lift on its upward
journey,then in how many ways can they do so?(Assume
they alight on different floors)

Answer 1

\(\large \color{black}{\begin{align}
& \normalsize \text{ In the Suniti Building in Mumbai there are 12 floors plus }\hspace{.33em}\\~\\
& \normalsize \text{ the ground floor.9 people get into the lift of the building }\hspace{.33em}\\~\\
& \normalsize \text{ on the ground floor.The lift does not stop on the first floor.}\hspace{.33em}\\~\\
& \normalsize \text{ If 2,3 and 4 people alight from the lift on its upward }\hspace{.33em}\\~\\
& \normalsize \text{ journey,then in how many ways can they do so?(Assume}\hspace{.33em}\\~\\
& \normalsize \text{ they alight on different floors)}\hspace{.33em}\\~\\
& a.)\ 11C3 \times 3P3 \hspace{.33em}\\~\\
& b.)\ 11P3 \times 9C4 \times 5C3 \hspace{.33em}\\~\\
& c.)\ 10P3 \times 9C4 \times 5C3 \hspace{.33em}\\~\\
& d.)\ 12C3 \hspace{.33em}\\~\\
\end{align}}\)

Answer 2

We can select the three floors in 11P3 .

Then of the 9 people four can leave in 9C4 ways

Three of the remaining 5 can be selected in 5C3 ways

so 11p3*9c4*5c3

Answer 3

I am having difficulty in interpreting the question

Answer 4

well you see in 11P3 order is important

Answer 5

in 9P3 order doesnt matter any way would be fine

Answer 6

does that make sense ?

Answer 7

see there is total of 13 floors 12+ ground floor

Answer 8

i know order is important in permutation and order isn't important in combination

Answer 9

11p3 where this come from ?

Answer 10

i am coming to that

Answer 11

because you see they are already on the ground level and they skip the first floor

Answer 12

so 13 -2 =?

Answer 13

11

and 3 ?

Answer 14

3 is no of ppl leaving the lift

Answer 15

srry its not 3 ppl its 3 floors

Answer 16

i was thinking about 5C3

Answer 17

ok and how come 9C4

Answer 18

now selecting 4 ppl from 9 in 9C4

Answer 19

why r u selecting only 4 people

Answer 20

( if 2, 3 and 4 people alight from the lift)*

Answer 21

now only 8 remaining so now selecting 3 from remaining 5 in 5C3

Answer 22

ok in 11C3 , 11 floors and the reason i choose 3 floors because (2,3 and 4 ppl alight from the lift)

Answer 23

still need help?

Answer 24

yes

Answer 25

about 9C4 and 5C3