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Answered by varadad25
6

Question:

The first and last term of AP are 17 and 350 respectively. If the common difference is 9, how many terms are there and what is theri sum?

Answer:

The number of terms of the AP is 38.

The sum of the first 38 terms of the AP is 6973.

Step-by-step-explanation:

We have given that,

The first and last term of an AP are 17 & 350 respectively.

The common difference of the AP is 9.

We have to find the number of terms and their sum.

Here,

  • a = t₁ = 17
  • tₙ = l = 350
  • d = 9

Now, we know that,

tₙ = a + ( n - 1) * d - - [ Formula ]

⇒ 350 = 17 + ( n - 1 ) * 9

⇒ 350 = 17 + 9n - 9

⇒ 350 = 17 - 9 + 9n

⇒ 350 = 8 + 9n

⇒ 9n = 350 - 8

⇒ 9n = 342

⇒ n = 342 ÷ 9

n = 38

Now, we know that,

Sₙ = ( n / 2 ) [ a + l ] - - [ Formula ]

⇒ S₃₈ = ( 38 / 2 ) [ 17 + 350 ]

⇒ S₃₈ = 19 * 367

S₃₈ = 6973

∴ The number of terms of the AP is 38.

The sum of the first 38 terms of the AP is 6973.

Answered by Anonymous
54

Number of terms in A.P is 38.

Sum of numbers in A.P is 6973.

Question :-

The first and last term of A.P are 17 and 350 respectively. If the

common difference is 9. How many terms are there and what is sum?

Given :-

First term of the A.P (a) = 17

Last term of the A.P (l) = 350

Common difference (d) = 9

To Find :-

Find number of terms (n) and Sum of term (Sn)

Formulas Applied :-

n = ( \frac{l - a}{d} ) +  1

 s_{n} =(  \frac{n}{2})  (a + l)

Solution :-

As by the formula let's find the number of terms (n)

n = ( \frac{l - a}{d} ) + 1

n = ( \frac{350 - 17}{9} ) +  1

n = ( \frac{333}{9} ) + 1

n = 37 + 1 \\ n = 38

Now Find the value of sum of terms (Sn) by given formula ,

s_{38} = ( \frac{n}{2} )(a+ l)

 s_{38} =  (\frac{38}{2} )(19 + 350)

 s_{38} = (19)(367)

s_{38} = 6973

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