Latest Elitmus Aptitude Question SOLUTION: 1,3,6,10,15,21,28........................so on up to 300 terms then find the sum

• Placement Papers
• /
• Elitmus
• /
• Numerical Ability
• /
• Sequence and Series

Elitmus Question Papers:

(#M40038313) ELITMUS Numerical Ability question Aptitude Keep an EYE

1,3,6,10,15,21,28........................so on up to 300 terms then find the sum

Asked In Elitmus T.VIGNESWARA REDDY (10 years ago)

Unsolved Read Solution (9)

Is this Puzzle helpful?   (8)   (0) Submit Your Solution Sequence and Series

Read Solution (9) :

Saraswathy  (10 years ago)

1 ,3, 6, 10 is of the form n*(n+1)/2
n = 300
nth term = 300*(301)/2 = 45150
Then sum of these terms 1+3+6+10+15+......45150 ll be
Sum of n*(n+1)/2 terms
Sum of n*(n+1)/2 terms = 1/2* sum of [n^2 + n] terms
Sum of n^2 terms => n(n+1)(2n+1)/6
sum of n terms => n(n+1)/2
So Sum ll be 1/2 * [n(n+1)(2n+1)/6 + n(n+1)/2]
n(n+1)(2n+4)/12
n = 300
So 300(301)(604)/12 = 4545100

Ans : 4545100

Is this solution Helpfull? Yes (38) | No   

Mohit Anand  (10 years ago)

each term in the series follows the equation-n(n+1)/2, where n is the position
therefore for the sum of 300 terms of the series , we will apply summation over n(n+1)/2,
hence it will expand to-- ((n(n+1)(2n+1))/6)+(n(n+1)/2)
which will compute to 300*301*604/12
=4545100

Is this solution Helpfull? Yes (8) | No (1)  

raushan kumar  (10 years ago)

ans==4545100

Is this solution Helpfull? Yes (3) | No (3)  

mareeswari  (10 years ago)

sn=n(a+l)/2.....
n=300,a=1,l=300
sn=300(301)/2
ans=45150

Is this solution Helpfull? Yes (3) | No (4)  

VIJAY SINGH  (9 years ago)

=1+3+6+10+15+21+28+36+.............................up to 300 terms
=4+16+36+64+..................................up to 150 terms
=2^2+4^2+6^2+8^2+...........................up to 150 terms
=2^2*(1^2+2^2+3^2+4^2...........................up to 150 terms)
=4*(n*(n+1)*(2*n+1)/6)
put n=150
=2*(150*151*301)/3
=4545100

Is this solution Helpfull? Yes (3) | No   

Goldi kumari  (10 years ago)

n=300 and a=1 and d=1 so now we no the formula of ap series n/2[2a+(n-1)d]
300/2[2*1+(300-1)*1]
45150

Is this solution Helpfull? Yes | No (5)  

ritwik misra  (10 years ago)

can someone tell me wat will be d diagram..i am got getting the question properly

Is this solution Helpfull? Yes | No   

sivakumarvalavala  (10 years ago)

n=300,a=1,d=1,(the diffrence between successive terms in A.P..1,3-1,6-3,10-6,15-15....) we know the formula.sum of the nth terms in A.P=n/2(a+l)
=300/2(1+300)=45,150

Is this solution Helpfull? Yes | No (2)  

Kumar Anmol   (9 years ago)

term are in the of n*(n+1)/2
sum of n^2 is n*(n+1)*(2*n+1)/12
sum of n term is n*(n+1)/2
so, sn=(n*(n+1)*(2*n+1)/12+n*(n+1)/2)/2
so ans 4545100

Is this solution Helpfull? Yes | No   

Please Login to Read Solution.