Question

find the sum of integers between 10 and 500 which are divisible by 7
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Answer 1

Answer:

⇒70

Step-by-step explanation:

first term is 14

last term is 497

tn=a+(n-1)d

497=14+7n-7

490=7n

490/7=n

70=n

Answer 2

AP is 14,21,28.....497

a=14 ,d=7, an=497

an = 497

a+(n-1)d=497

14+(n-1)7=497

(n-1)7=497-14

(n-1)7=183

n-1=183/7

n=69+1

n=70

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

S70=70/2(2(14)+(70-1)7)

=35(28+(69)7)

= 35(28+483)

= 35(511)

=17885