Question

In the sequence, 1, (2, 3), (4, 5, 6), (7, 8, 9, 10) …….. of sets, the sum of elements in the 50th set is-

• A. 62525
• B. 65225
• C. 56255
• D. 557625

Answer 1

Answer: (A)

62525

Answer 2

Let the first term of n^th row T_n = an² + bn + c

Put n = 1, 2, 3, & get a, b, c then T_n =$\frac { 1 } { 2 }$n² –$\frac { 1 } { 2 }$n + 1

Then sum of all term of n^th set is

= = $\frac { \mathrm { n } } { 2 }$ (n² + 1)

Put n = 50 and get sum of element of 50^th set

= $\frac { 50 } { 2 }$ (50² + 1) = 62525