Question

in an AP 2nd and 3rd terms are 24 and 30 respectively find the sum of 51 terms of
AP.​

Answer 1

Answer:

a

2

14

a

3

18

Common difference,

d=

a

3

a

2

18−

14=

4

Now

a

2

a+ d= 14

a+ 4= 14

a= 10

Now, sum of 51 terms

S

n

2

n

(2a+

(n− 1)d)

S

51

=

2

51

(2(10)+ (51− 1)4)

=

2

51

(20+ 200)

=

2

51×220

= 51× 110= 5610

S

51

= 5610

Answer 2

Answer:

Correct option is A)

a2=14 and a3=18

Common difference, d=a3−a2=18−14=4

Now 

a2=a+d=14

a+4=14

a=10

Now, sum of 51 terms

Sn=2n(2a+(n−1)d)

S51=251(2(10)+(51−1)4)

=251(20+200)

=251×220

=51×110=5610

S51=5610

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SIMILAR QUESTIONS

If the sum of first p terms of an A.P. is equal to the sum of the first  q terms, then find the sum of the first (p+q) terms.

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Find the sum of the first 11 terms of the A.P: 2,6,10,14,....

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>