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(#M40039749) TCS Numerical Ability question Keep an EYE

what will be the 9th & 99th number of the following series:
2, 10, 26, 50........................

Asked In TCS ranjan kumar (10 years ago)

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Kolluru Nagalakshmi  (10 years ago)

if we observe pattern
2nd number is (8*1)+2
3rd number is (8*2)+(8*1)+2
4th number is (8*3)+(8*2)+(8*1)+2
hence 9th number is (8*8)+(8*7)+...+(8*2)+(8*1)+2
=8(8+7+6+5+4+3+2+1)+2
=8((8*9)/2)+2 (sum of n numbers)
=288+2
=290
99th number is (8*98)+(8*97)+(8*96)+...+(8*2)+(8*1)+2
=8(98+97+96+...+2+1)+2
=8((98*97)/2)+2
=38808+2
=38810
9th number is 290 & 99th number is 38810

Is this solution Helpfull? Yes (36) | No (4)  

Narasapu Hari prasad  (10 years ago)

This is in the form
1^2+1,,3 ^2,,5^2+1,,7^2+1
so 9th number will be 17^2+1
and 99th number is =197^2+1

Is this solution Helpfull? Yes (19) | No   

Priyanshu Singh  (10 years ago)

Is form a quadratic eqn ax^2 +bx + c =tn
Implies a+b+c=2
4a+2b+c=10
9a+3b+c=26
Solving u get a 4 b -4 and c 2
Eqn bcm 4x^2-4x+2
Put x 9 for ninth term .it will be 290

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

surbhi dubey  (10 years ago)

290 for 9th term
i.e
9*2=18-1=17=17*17+1=289+1=290
now
99*2=198-1=197
197*197+1

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SUDIPTA BOSE  (4 years ago)

t9=2+(9-1)*8=66
t99=2+(99-1)*8=786

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