Maths question (Series)

[Amy Bloom]

Anyone can provide me the workings of the following question:

Find the sum of all integers from 1 to 200 inclusive that are not multiples of 5.
Answer: 16000

thanks in advance.

 

[syed1995]

I found this question to be good so i am attempting it..

Sum of All 200 numbers
Sn=(a+(n-1)d)*n/2
(1+199*1)*200/2
(200)*100
20000 Answer

Sum of Multiples of 5 between 5 and 200..
Sn=(a+(n-1)d*n/2)

200/5 there are 40 numbers in total. so n=40

Sn=(5+39*5)*40/2
Sn=(200)*20
Sn=4000

(Sum Of All 200 Numbers) - (Sum Of Multiples of 5).. should give you the answer for (Sum of Those numbers which are not multiples of 5)
20,000-4000 = 16000 Answer

I hope you got the method.. If you need any help ask me.

Cheers

 

[Amy Bloom]

syed1995 Jazak Allah brother, i understood it all, so clear and concise. May Allah reward you. ameen.

 

[syed1995]

syed1995 Jazak Allah brother, i understood it all, so clear and concise. May Allah reward you. ameen.

No problem mate You're welcome!