a series of natural number 1+2+3+4+5+6+7+8+9+10 is divisibel by 11 so we has to find how many such series is possible upto n where n is less than 1000.  Choose one: A) 90 B) 99 C) 180 D) 96 E) 92
the total multiple of 11 less then 1000 are 90 .   and for every multiple there are two such series which are divisible by 11.   . .   . sum of series = n(n+1)/2   for multiple 11 we can take n=10 and 11   for 22 '' '' ''' n=21 and 22   and so on and for 990 multiple of 11 we can take n=989 and 990   so total series formed are 90*2= 
<gadget id="calculator">90*2</gadget>
<output>180</output>
180   ANSWER:180
<result>C</result>
a series of natural number 1+2+3+4+5+6+7+8+9+10 is divisibel by 11 so we has to find how many such series is possible upto n where n is less than 1000.