Question
Find the sum of all natural numbers lying between 100 and 1000, which are mutliples of 5.
Solution
All the natural numbers between 100 and 1000 which are multiples of 5 are:
105, 110, 115, ......, 995.
Let 
denote their sum, i.e., ![<pre>uncaught exception: <b>mkdir(): Permission denied (errno: 2) in /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php at line #56mkdir(): Permission denied</b><br /><br />in file: /home/config_admin/public/felixventures.in/public/application/css/plugins/tiny_mce_wiris/integration/lib/com/wiris/util/sys/Store.class.php line 56<br />#0 [internal function]: _hx_error_handler(2, 'mkdir(): Permis...', '/home/config_ad...', 56, Array)
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#6 {main}</pre>](/application/zrc/images/qvar/MAEN11032652-1.png)
Here, a = 105, d = 110 - 105 = 5, 
i.e., a + (n - 1)d = 995 or 105 + (n - 1)5 = 995
or 5n + 100 = 995 or 5n = 995 - 100 = 895
or 
∴ 
