Question

find the sum of AP 1,3,5,.......67​

Answer 1

Hiii !

First term = a₁ = 1

Second term = a₂ = 3

Common difference = d = a₂- a₁ = 3 - 1 = 2

Last term = an = 67

an = a+ (n-1)d

67 = 1 + (n-1)2

67= (n-1)2

68/2 = n - 1

34 = n - 1

n = 35

No: of terms = n = 35

Sum = Sn

Sn = n/2 [a + an]

     = 35/2 [ 1 + 67]

     = 35/2 [ 68]

     = 35×34

Sum = 1190

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Answer 2

Answer:

The sum of the A.P is 1156..

Explaination:

a = 1

d = 2

an = 67

Sn = n/2 {a + an}

For that we need to find n,

An = a + (n-1) d

67 = 1 + 2n - 2

67 = -1 + 2n

67 + 1 = 2n

68 = 2n

n = 68/2

n = 34....

Now,

Sn = n/2 {a + an}

Sn = 34/2 ( 1 + 67 )

Sn = 17 ( 68 )

Sn = 1156

Hope it helps you... Bro....