find the sum of all integers between 84 and 719 which are multiple of 3 Question find the sum of all integers between 84 and 719 which are multiple of 3 in progress 0 Math Lydia 1 month 2021-08-12T07:43:26+00:00 2021-08-12T07:43:26+00:00 2 Answers 0 views 0

## Answers ( )

Answer:Sn= 254551 is the required answer.Step-by-step explanation:As we have to find the sum of all integers between 84 and 719

So the integers will be :- 85 , 86 , 87 , …. , 718

So let a1 = 85 , a2 = 86 and a3 = 87

a2 – a1 = 86 – 85 = 1

a3 – a2 = 87 – 86 = 1

As , a2-a1 = a3-a2 , so the sequence forms a AP with a = 85 andd = 86 – 85 = 1 and an = 718So by the formula , tn = a + ( n – 1 ) d

⇒718 = 85 + ( n – 1 ) 1

⇒718 = 85 + n – 1

⇒718 = 84 + n

⇒n =718 – 84

⇒

n = 634Now as we also know the number of terms n = 634

so by the formula , Sn =

⇒ Sn =

⇒ Sn = 317 [ 170 + 633 ]

⇒ Sn = 317 [ 803 ]

⇒

Sn= 254551Answer:b6sitzdo7f7zkr 7giicyIpu