Author Topic: Arithmetic series (Read 1125 times) Tweet Share

cleo_xo · « **on:** September 01, 2010, 06:04:23 pm »

Can anyone please help?
Find the sum of all integers divisible by 3 which lie between 200 and 400
Find the sum of all integers divisible by 6 which lie between 200 and 400
Thanks a lot

the.watchman · « **Reply #1 on:** September 01, 2010, 06:24:17 pm »

(a) Find the first applicable number, 201, and last, 399

Finding number of terms, $t_n = t_1 + (n-1)d$

So $399=201+(n-1)3$ , $n=67$

Hence $S_{67}= \frac{67}{2} (t_1 + t_n) = \frac{67}{2} (201+399) = 20100$

Try a similar method for (b)

Nomvalt · « **Reply #2 on:** September 01, 2010, 06:52:46 pm »

Is this relevant to spesh?

the.watchman · « **Reply #3 on:** September 01, 2010, 07:22:27 pm »

Quote from: Nomvalt on September 01, 2010, 06:52:46 pm

Is this relevant to spesh?

Not to my knowledge, GMA only?

cleo_xo · « **Reply #4 on:** September 01, 2010, 07:30:07 pm »

thank you !!!

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Author Topic: Arithmetic series (Read 1125 times) Tweet Share

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