Question

If in an A.P., first term is 13 and common difference is - 4 then sum of its first 10 terms is (A) 50 (B). - 50 (C) 30 (D) -


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Answer 1

Answer:

-50

Step-by-step explanation:

Given that first term of AP denoted by a is 13. Common difference denoted by d is -4. We have to find the sum of first 10 terms.

An AP is a sequence of numbers in which each successive term differs from the preeceeding term by a common difference which remains constant throughout the progression.

Sum of first n terms of AP is given by,

Sn = n/2 [ 2a + ( n - 1 ) d ]

Here

• Sn = Sum
• n = Number of terms
• a = First term
• d = Common difference

By substituting the known values in the formula of sum, we get :

⇒ Sn = 10/2 [ 2(13) + ( 10-1 ) ( -4 ) ]

⇒ Sn = 5 [ 26 + 9(-4) ]

⇒ Sn = 5 [ 26 - 36 ]

⇒ Sn = 5 [ -10 ]

⇒ Sn = -50

Hence the sum of first 10 terms of the AP is -50.

Option (B) is correct

Answer 2

Answer:

Your answer is -50

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