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Question 1. Asked on :29 December 2018:01:00:20 AM

If the sum of first 7 terms of an AP is 49 and that of 17 terms is 289, find the sum of first n terms.

-Added by ATP Admin Mathematics » Arithmetic Progressions

Answer:

S7 = 7/2(2a + 6d) 

=> 49 = 7a + 21d

=> 7 = a + 3d   ------------ (i) 

S17 = 17/2 (2a + 16d) 

=> 289 = 17a + 136

=> 17 = a + 8d --------------  (ii) 

Substracting equation (i) from (ii) 

we have ... 

17 - 7 = a - a + 8d - 3d 

10 = 5d 

d = 10/5 

d = 2 

Putting the value in Equation (i) 

7 = a + 3d 

7 = a + 3 x 2 

a = 7 - 6 

a = 1 

Sum of first n terms = n/2 [2a + (n - 1) d]

= n/2 [2x 1 + (n - 1)2] 

= n/2 [2 + 2n - 2 ]

= n/2 (2n) 

= nxn = n2

-Answered by Harshita Rathore On 26 August 2019:03:25:54 PM

Question 2. Asked on :28 December 2018:11:00:50 PM

How many terms of the AP : 9, 17, 25, . . . must be taken to give a sum of 636?

-Added by ATP Admin Mathematics » Arithmetic Progressions

Answer:

 A.p= 9,17,25

a=9

d=17-9

=8

Sum of n terms=n÷2[2a+(n-1)d


636=n÷2[2(9)+(n-1)8]

636=n÷2[18+8n-8]

636=n÷2[10+8n]

1272=10n+8n^2

8n^2+10n-1272=0

2[4n^2+5n-636]=0

4n^2+5n-636=0

4n^2+53n-48n-636=0

n(4n+53)-12(4n+53)=0

(n-12)(4n+53)=0

n-12=0

n=12


12 terms must be given to sum of 636

-Answered by Master Purushottam On 22 August 2019:08:54:23 PM

Question 3. Asked on :28 December 2018:10:59:05 PM

What are the various uses of concave mirror?

-Added by ATP Admin Science » Light and Reflection

Answer:

Use of cancave mirror; 

(i)    Concave mirrors are commonly used in torches, search-lights and vehicles headlights to get powerful parallel beams of light.

(ii)    They are often used as shaving mirrors to see a larger image of the face.

(iii)   Concave mirrors are used to see large images of the teeth of patients by the dentists.

(iv)   Large concave mirrors are used to concentrate sunlight to produce  heat in solar furn

-Answered by Nishant Verma On 06 October 2019:09:46:42 AM

Question 4. Asked on :28 December 2018:09:14:15 PM

what is politics? why do we need it?

-Added by ATP Admin Political Science » Politics

Answer:

Politics is the process of making decisions that apply to members of a group. We need it because of the politics is the part of state and regarding to people life.

-Answered by Nishant Verma On 17 October 2019:02:36:03 PM

Question 5. Asked on :27 December 2018:07:24:55 PM

कोपरा क्या है?

-Added by ATP Admin Economics » उपभोक्ता अधिकार

Answer:

 उपभोक्ता सुरक्षा अधिनियम 1986.


-Answered by Nishant Verma On 06 October 2019:09:48:07 AM

Question 6. Asked on :27 December 2018:07:12:35 PM

भारत में पहला पटसन उद्योग कब स्थापित हुआ था?

-Added by ATP Admin Geography » विनिर्माण

Answer:

भारत में जूट का प्रथम कारखाना सन 1859 में स्कॉटलैंड के एक व्यापारी जार्ज ऑकलैंड ने बंगाल में श्रीरामपुर के निकट स्थापित किया और इन कारखानों की संख्या 1939 तक बढ़कर 105 हो गई

-Answered by Nishant Verma On 06 October 2019:09:48:17 AM

Question 7. Asked on :27 December 2018:03:52:45 PM

Who discovered the nucleus of an Atom?

-Added by ATP Admin Science » Atom and Its Structure

Answer:

Nucleus of an Atom is  discovered by Ernest Rutherford 

-Answered by Shruti Srivastva On 15 July 2020:12:54:43 PM

Question 8. Asked on :27 December 2018:03:42:49 PM

Who was the last Viceroy of India?

-Added by ATP Admin History » Indian History

Answer:

Last Viceroy of India is Lord Mountbatten.

-Answered by Shruti Srivastva On 15 July 2020:12:56:08 PM

Question 9. Asked on :26 December 2018

Why cell is called structural and functional unit of body?

-Added by shyam Babu Science » cell

Answer:

Cells are called the structural and functional unit of life because all the living organisms are made up of cells and also all the functions taking place inside the body of organisms are performed by cells.

-Answered by Nishant Verma On 06 October 2019:09:48:53 AM


 

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