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Maths, Addmaths and Statistics: Post your doubts here!

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Q. The cost of a TV and a radio together is Rs. 4220. The Cost of TV set is Rs. 20 more than 6 time
that a radio. What is the cost of the radio?

A.Rs 1000
B. Rs 100
C, Rs 700
D, Rs 2500
 
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Anyone please answer this question. I've got my mock tomorrow and I don't even have a vague idea how to solve this problem:
A shelf is to contain 7 different books, of which 4 were written by Dickens and 3 by Hardy. Find the number of arrangements in which the first two books at the left-hand end are by the same author.
scouserlfc PhyZac Suchal Riaz : Plz give it a try
 
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Anyone please answer this question. I've got my mock tomorrow and I don't even have a vague idea how to solve this problem:
A shelf is to contain 7 different books, of which 4 were written by Dickens and 3 by Hardy. Find the number of arrangements in which the first two books at the left-hand end are by the same author.
scouserlfc PhyZac Suchal Riaz : Plz give it a try
I am not sure of my answer..
My answer is 2160

Incase it is right...here is my way

now there is 7 places and they want 2 books at one side to be of same author
so it can be Dickens or Hardy
if Dickens then it will be 4P2 (4 permutate 2 ) and left will be 5 books thus x5! (into five factorial )
so answer will be 1440

if Hardy then it will be 3P2 and left will be 5 books thus x5!
so answer will be 720

1440 + 720 = 2160
 
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I am not sure of my answer..
My answer is 2160

Incase it is right...here is my way

now there is 7 places and they want 2 books at one side to be of same author
so it can be Dickens or Hardy
if Dickens then it will be 4P2 (4 permutate 2 ) and left will be 5 books thus x5! (into five factorial )
so answer will be 1440

if Hardy then it will be 3P2 and left will be 5 books thus x5!
so answer will be 720

1440 + 720 = 2160
Oh my goodness! Your answer is absolutely right!!!!!
You're a life saver, believe me. Thank you so much for the reply. (y):)
 
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My answer of permutation and combination never comes true. i know everything. read book. solved most of the book. but when it comes to past papers i m not able to solve it. any notes, videos or assistance is highly appreciated.
 
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My answer of permutation and combination never comes true. i know everything. read book. solved most of the book. but when it comes to past papers i m not able to solve it. any notes, videos or assistance is highly appreciated.
try khanacademy, well permutation and combination are considered one of the hardest chapter after relative velocity, as most of the answer is comes different from the other pupils,unlike probability its really hard to think it practically when u deal with numbers
 
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try khanacademy, well permutation and combination are considered one of the hardest chapter after relative velocity, as most of the answer is comes different from the other pupils,unlike probability its really hard to think it practically when u deal with numbers
try khanacademy, well permutation and combination are considered one of the hardest chapter after relative velocity, as most of the answer is comes different from the other pupils,unlike probability its really hard to think it practically when u deal with numbers
yeah, i get really confused when to apply permutations and when to apply combinations...
but the most of the time , answer comes wrong, no matter what...
 
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yeah, i get really confused when to apply permutations and when to apply combinations...
but the most of the time , answer comes wrong, no matter what...
ikr, and here's the most hardest permutaiton and combination question : A box contains sweets of 6 different flavours . There are atleast 2 sweets of each flavour . A girl selects 3 sweets from the box . Given that these 3 sweets are not all of the same flavour. Calculate the number of different ways she can select her 3 sweets? ..


according to er, 90% answer's were wrong. here's the answer : 2(6C2) + 6C3 = 50
6C2 ways for there to be 2 flavors chosen. 2 possibilities for which flavor is chosen twice.
6C3 ways for there to be 3 flavors chosen.

If you don't multiply the 6C2 by 2, then you get 35. It's easy to forget that step. {cherry, cherry, blueberry} is different than {cherry, blueberry, blueberry}

Another way altogether:
6 multichoose 3 = (6+3-1) C 3 = 8C3 = 56
Then subtract the 6 possibilities of all the same flavor: 56 - 6 = 50
 
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try khanacademy, well permutation and combination are considered one of the hardest chapter after relative velocity, as most of the answer is comes different from the other pupils,unlike probability its really hard to think it practically when u deal with numbers
these is rarely any video that i have not seen on khan academy :p
 
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