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Mathematics: Post your doubts here!

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Rahul Athreya

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a woman finds that she only gets home from work in time to see the start of the programme on average twice in a working week of five days, each

day being equally likely.

a) Find the probability that in a given working week she will be home in time to see the start of the programme:

iii) on 4 consecutive days but not the fifth.

b) Find the mean and standard deviation of the number of times she is home to see the start of the

programme during a period of six working weeks.

Thanks guys <3
 
DragonCub

DragonCub

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areeba240 said:
the ans is wrong........
View attachment 61586
i got the equation givein in part (i) if possible plzz tell me how to find least value using this equation View attachment 61587
Click to expand...

Uh I'm soooo sorry, misread a tiny part of the question and that happened...

I've corrected my work (edited my original reply), and arrived at the same answer provided by the marking scheme.
Should not be any more errors there.

Again, sorry about the wrong answer :p
 
F

FrostBite92

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Can anyone help with this? Can't wrap my head around this problem.

A staff car park at a school has 13 parking spaces in a row. There are 9 cars to be parked.
i. How many Different arrangements are there for parking the 9 cars and leaving 4 empty spaces?
ii.How many different arrangements are there if the 4 empty spaces are next to each other?
iii. if the parking is random, find the probability that there will not be 4 empty spaces next to each other.

Any help would be appreciated.
 
DragonCub

DragonCub

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i_try9621 said:
In i, Why do we need two points that are on both planes?
Click to expand...

We need two points because we need to find the line's vector. The fastest way to find the vector is to obtain two points on the line.

If you are interested in another method of determining the vector, you can use the normal vectors of P1 and P2.
If the vector is parallel to both planes, then it must be perpendicular to both planes' normal vectors, n1 and n2
Thus you can use cross product, n1 x n2, the product is the parallel-to-both-planes vector we are looking for.

i_try9621 said:
Also couldn't it be that the planes were skewed?
Click to expand...

In a 3-dimension space, only lines can be skewed to each other. Planes can only be parallel or intersecting.
 
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