How to find proportion of Four numbers

If A : B = 2 : 3, B : C = 4 : 5 and      C : D = 6 : 7,    what is A  : D  ?

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What is next terms in the series ?

What is next terms in the series ?

Let us solve next number in sequence puzzle
15,29,56,108,208,????
Here 1st term is 15, To find out 2nd term if we multiply the 1st term With 2 and subtract 1 from it, i.e (15 *2) -1  = 29
To find 2nd term we have to multiply the previous term with 2 and subtract 2 (double the previous time) from it
I.e 29*2 - 2 = 56
To find 3rd term we have to multiply the previous term with 4   and subtract 2  (double the previous time) from it
I.e 56*2 - 4 = 108
To find 4th term we have to multiply the previous term with 8 (double the previous time) and subtract 2 from it
I.e 108*2 - 8 = 208
Similarly 5th term can be calculated as
multiply the previous term with 2 and subtract  subtract 2 (double the previous time) from it
I.e 208*2 - 16 = 400
Next term 400*2 - 32 = 768

Next term  768*2 - 64 = 1472
Next term  1472*2 - 128 = 2816
Or we can write it in another form as follows
15+(15–1) = 29
29+(29–2) = 56
56+(56–4) = 108
108+(108–8) = 208
208+(208–16) = 400
400+(400–32) = 768

768+(768–64= 1472

1472+(1472-128) =2816

And similarly this trend follows


What’s the next number in the sequence 0, 2, 6, 12?


We can get the answer in two  ways


1st way


1 * (1–1) = 0 ( 1st term)

2 * (2–1) = 2 (2nd term)

3 * (3–1) = 6 (3rd term)

4 * (4–1) = 12 (4th term)

5 * (5–1) = 20 (5th term) 

Next term must be  20
Similarly 
6 * (6–1) = 30  (6th term)

7 * (7–1) = 42  (7th term)


2nd Way



1^2 –1 = 0

2^2 – 2 = 2 

3^2 – 3 = 6

4^2 – 4 = 12 

5^2 – 5 = 20 
Next term must be  20
Similarly 

6^2 – 6 = 30 

7^2 – 7 = 42

Can you solve this  Series: 30, 31, 28, 33, 26, 35, … What number should come next?


We can split this sequence into two series by picking alternate numbers from the given sequence. 
30, 31, 28, 33, 26, 35, …
1st  one is 30,  28, 26, … and 2nd one is  31, 33,  35, …
Now after careful analysing the 1st sequence ,it next terms should be  with decrease of  2 ,we get other terms as follows 
30,  28, 26, 24,22,20 …
And after careful analysing the 2nd  sequence ,it next terms should be  with increase of  2 ,we get other terms as follows 
31, 33,  35, ,37,39,41…

26-2 = 24.
So the text terms should be 30, 31, 28, 33, 26, 35, 24,37,22 

24 is the next number in the required sequence

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HOW TO ADD 1 TO 1000 NUMBERS VERY EASILY

HOW TO ADD 1 TO 1000 NUMBERS VERY EASILY

If you want to add 1 to 1000 then follow these two steps
Add 1 to last number 

2 Multiply last number and it's next numbers then divide by 2 . And thats it  .

अगर आप 1 से लेकर किसी भी अंतिम संख्या को जोड़ना चाहते हो तो सबसे पहले अंतिम संख्या में एक जोड़ दें फिर अंतिम संख्या और उससे आगे बाली संख्या को गुणा करके 2 से भाग दे दें ,आप इस तरह से कितनी भी शंख्ययाओं का जोड़ एक दम से कर सकते हो

उदाहरण

If we have to add 1st 50 numbers then  Multiply 50 with 51 and divide the product with 2 and it is the sum of 1st 50 natural numbers 

 अगर हम 1 से 50 को जोड़ना चाहें तो 50 और 51 गुना करके 2 से भाग देंगे
1 +2+3+4+5+6+7+……+50 =(50×51)÷2 = 25×51=1275
अगर हम 1 से 100 को जोड़ना चाहें तो 100 और 101 गुना करके 2 से भाग देंगे
1+2+3+4+5+…….+100=( 100×101) ÷2 =50×101=5050
अगर हम 1 से 1000 को जोड़ना चाहें तो 1000 और 1001 गुना करके 2 से भाग देंगे
1+2+3+4+5+…….+1000 =(1000×1001)÷2 = 500×1001= 500500
अगर हम 1 से 2000 को जोड़ना चाहें तो 2000 और 2001 गुना करके 2 से भाग देंगे
1+2+3+4+5+…….+2000=( 2000×2001)÷2 =1000×2001 = 2001000



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HOW TO FIND SHORTEST DISTANCE BETWEEN TWO LINES

SHORTEST DISTANCE BETWEEN TWO LINES

1st of all we shall find out shortest distance between two Parallel lines.

Problem 1

Consider two parallel lines whose equations in vector form are given by
HOW TO FIND SHORTEST DISTANCE BETWEEN TWO LINES

 Now comparing these equations with standard form , and write

 , and  vectors ,we get
HOW TO FIND SHORTEST DISTANCE BETWEEN TWO LINES

Now applying this formula to find the shortest distance between two lines .
HOW TO FIND SHORTEST DISTANCE BETWEEN TWO LINES
As it is clear from formula , we have to find cross product of  and  and then magnitude of vector 

HOW TO FIND SHORTEST DISTANCE BETWEEN TWO LINES

Now find the magnitude of  × vector
HOW TO FIND SHORTEST DISTANCE BETWEEN TWO LINES
                                 =√(81)+(196)+(16)
                                 =√293
Magnitude of 
HOW TO FIND SHORTEST DISTANCE BETWEEN TWO LINES
                    = √49
           = 7
Putting all these values in  the formula of Shortest Distance between two lines .
HOW TO FIND SHORTEST DISTANCE BETWEEN TWO LINES
Now Find distance between two skew lines i.e. Lines which are not Parallel lines.

Problem 2

Consider two parallel lines whose equations in vector form are given by
 Now comparing these equations with standard form , and write

 , and  vectors ,we get
 Now applying this formula to find the shortest distance between two lines 

 Now find cross product and then  magnitude of these two vectors


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Find two positive numbers whose sum is 16 and sum of whose cube is Minimum


Show that of all the rectangles inscribed in a circle of given radius . The Square has maximum Area.


Solutions


Let ABCD be rectangle which is  inscribed in a given circle of radius ‘r’
Show that of all the rectangles inscribed in a circle of given radius . The Square has maximum Area.
And Let θ be the angle between side of rectangle and Diameter of given circle.


Therefore from right angled  Δ ABC ,

We have 
  AB  = AC cosθ          ∵ AC = 2r
Let A(x) be the area of Rectangle ABCD
∴ A(x) = AB × BC
    A = (2r cos θ)(2r sin θ )
    A =  4r2 sin θ cos θ
    A = 2r2  (2sin θ cos θ)
    A = 2r2  (sin 2θ )

⇒ 2r2 2 (cos 2θ ) = 0 ,As r2 is constant
⇒cos 2θ = 0
⇒cos 2θ =cos (π/2)
⇒ θ = π/4
 =4r2  (-2sin 2θ 



∴ A has Maximum value at θ = π/4



Find two positive numbers whose sum is 16 and sum of whose cube is Minimum

Solution

Let us consider two numbers x and 16- x .
Then transforming our problem to mathematical form which says “sum of whose cube”  as follows
A (x) =   x3 + (16 - x)3…….. (1)
Differentiating both sides w .r. t  “x” , we get



     X = 8
So  x  =  8 will be the 1st required numbers if Double derivatives of A  w. r. t  ‘x’ comes to be positive at x = 8.
Differentiate (2)  w. r. t. ‘x’  .




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