Sequence And Series Question 150
Question: $ 11^{3}+12^{3}+….+20^{3} $
[Pb. CET 1997; RPET 2002]
Options:
A) A number is divisible by 5 if it ends in 0 or 5
B) Is an odd integer divisible by 5?
C) Is an even integer which is not divisible by 5
D) Is an odd integer which is not divisible by 5
Show Answer
Answer:
Correct Answer: B
Solution:
$ \sum\limits_{n=1}^{20}{(n^{3})}-\sum\limits_{n=1}^{10}{(n^{3})}=[ \frac{n(n+1)}{2} ]^{2}{n=20} - [ \frac{n(n+1)}{2} ]^{2}{n=10} $ Þ $ s_2={{[ \log ,5/3 ]}^{2}} $ = 44100 - 3025 = 41075.
BETA
