Problem Solving Strategies

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user15072279

02:48

How to solve this

4 hours later…

John Rennie

07:17

@user15072279 what is r in the equation (p/q)r ?

Nobody recognizeable

@JohnRennie hi

@JohnRennie had this question.

John Rennie

07:34

@Nobodyrecognizeable hi :-)

It's a long time since I did a crystallography course, but as I recall what determines the peak intensity is the interference between the x-rays scattered from the K atoms and the x-rays scattered from the Cl atoms.

If these are out of phase then the peak is suppressed.

1 hour later…

user15072279

08:38

@JohnRennie r is by mistake . Ignore it.

John Rennie

@user15072279 hi :-)

user15072279

Hey sir

John Rennie

I don't think there's a simple formula to give you the number of distinct rational numbers, but you can do it easily by an exhaustive search.

user15072279

sir , do you want to check my YouTube channel where I make my own music

Music Sri - Knock it down | Golden Hip hop |Official audio #Hip Hop #Music

►

John Rennie

For example start with p = 1, then q cannot be 1 because x has to be less than unity. So there are five possible numbers with q = 2 to 6. Yes?

@user15072279 hip hop isn't really my thing :-)

I like prog rock and indie music.

user15072279

08:41

@JohnRennie There are some more music videos also.

@JohnRennie k . Nice choice. I like reggae ,jazz and many more

@JohnRennie K. I got your answer point one

I got the answer and it’s correct.

I got the key point.

John Rennie

OK :-)

Anusha

09:38

@RishiNandhaVanchi what's ur exam date ?

RishiNandha Vanchi

09:56

24 morning shitf

I gotta start like 650 from home ajsksjal

Centre’s like more than 1hr from here

@JohnRennie oooooooh prog

Is it something like a lot of mathematicians and Physicists naturally like genres like prog, rock and metal XD

John Rennie

:-)

RishiNandha Vanchi

My math sir was a huge fan too

user15072279

10:16

@RishiNandhaVanchi All the best for the exam .

I still have 9-10 months

RishiNandha Vanchi

Thanks!

Good luck with your preps

user15072279

Guys , do you think the question that have some trick in them , imp questions should be written in th notebook you’re making your notes in or some other notebook where you write solutions for all the Q’s

YouKnowMe

10:58

@JohnRennie Hi :-)

John Rennie

@YouKnowMe hi :-)

YouKnowMe

> If the rightmost digit to be removed is 5,
then the preceding number is not changed
if it is an even number but it is increased
by one if it is an odd number. For example,
if 6.35 is to be rounded by removing 5,
we have to increase 3 to 4 giving 6.4 as
the result. However, if 6.25 is to be
rounded off it is rounded off to 6.2.

Do you know the logic behind this?

John Rennie

No. I would have rounded 6.25 to 6.3

I have never heard of the procedure you describe.

It's possible that it is done to keep averages the same.

YouKnowMe

@JohnRennie Averages?

John Rennie

Consider an example. Suppose we have the ten numbers 6.05, 6.15, 6.25, 6.35, 6.45, 6.55, 6.65, 6.75, 6.85 and 6.95.

The sum of the ten numbers is 65, so the average is 6.5.

Suppose we apply the simple rounding rule, then they all round up to 6.1, 6.2, ... , 7.0, and now the sum is 65.5 so the average is 6.55.

The rounding process has caused the average of the numbers to increase from 6.5 to 6.55. OK so far?

YouKnowMe

11:09

John Rennie

But now suppose we use the rule you describe. The first number, 6.05, rounds down to 6.0, while the second number, 6.15, rounds up to 6.2. OK so far?

YouKnowMe

:o Got it!

John Rennie

So doing it this way the rounding downs and rounding ups are going to cancel and keep the average the same.

I don't know if that is the reason for the procedure you describe, but it is certainly an advantage of it.

YouKnowMe

@JohnRennie Thanks:-)

Should I ask in Math room?

John Rennie

You could try ..

John Rennie

11:52

:57037873 hi :-)

user15072279

I have confusion in combinations. Can you help sir

Hi sir

@JohnRennie

cant we say that every multiple choice Q , there are 5 choices. 5*5*5*5

5 questions I meant

John Rennie

I'm busy answering another question for a few minutes ...

user15072279

@JohnRennie k sure

John Rennie

@user15072279 There are five questions, and there are four ways to answer each question. Yes?

user15072279

Yes

John Rennie

12:07

So for the first question there are 4 ways to answer, and for each of those ways there are 4 ways to answer the second question. So there are 4 x 4 ways to answer the first two questions. Yes?

user15072279

Yes.I did That way . Answer is 4^5 but I want to know where am I wrong I do it the second way

The new way I have written

where am I wrong

John Rennie

11 mins ago, by user15072279

cant we say that every multiple choice Q , there are 5 choices. 5*5*5*5

user15072279

yes

John Rennie

I don't understand what you are saying here ...

user15072279

there are 4 multiple choice options

Then , there are 5 Q

so , for every multiple choice option

there are 5 Q to be selected

@JohnRennie

John Rennie

12:11

OK, let's call the four options A, B, C and D.

user15072279

for option A , you can select 5 Q

John Rennie

Right

user15072279

5*5 *5 *5 for all Q

@JohnRennie

John Rennie

It's more complicated than that ...

user15072279

Ok but isn’t the way right

John Rennie

12:15

Because you could answer A to just Q1 or just Q2 or Q1 and Q2 or just Q3 or Q1 and Q3 and so on.

I'd have to sit down and think about how to do the calculation that way.

user15072279

Ohhh

if A is for Q 1

2,3,4 or 5

then B is for 1234

since you can’t tick all the options

5 *4*3*2

but that is still wrong

John Rennie

It's going to be complicated.

Basically it's a hard way to try and answer an easy problem.

user15072279

I know but I want to understand the concept

More deeper and 100% actually

John Rennie

I'd have to go away and think about how to do this.

user15072279

Ok. Thank you for your time sir . Thank you

John Rennie

12:22

:-)

4 hours later…

user586228

16:01

@JohnRennie Sir, for diffusion I have seen a form occuring very often..

It is referred to as $x^2/Dt=const$

I really do not understand what this form imlies...

implies..

Annamalai Sriram

16:31

@JohnRennie @satan29 Hi

after a longtime I am asking a doubt now

related to capacitors (again)

Could you tell me how to solve ?

Anusha

17:03

@AnnamalaiSriram use node potential method based on charge conservation

Annamalai Sriram

@Anusha why charge is conserved here(why q1 + q2 + q3 ) = 0

toppr.com/ask/question/…

John Rennie

17:20

@AnnamalaiSriram the point O isn't connected to any external wire, so charge cannot flow in or out of that part of the circuit.

When we start all the capacitors are uncharged so the total charge at O is zero, and since no charge can flow in or out of O the total charge has to remain zero.

Annamalai Sriram

@JohnRennie Ok

Thanks

John Rennie

:-)

Are you happy with this problem now?

Annamalai Sriram

Hmm yes

John Rennie

OK :-)

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