1
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
The sum of the first 20 terms of the series

$$1 + {3 \over 2} + {7 \over 4} + {{15} \over 8} + {{31} \over {16}} + ...,$$ is :
A
$$38 + {1 \over {{2^{19}}}}$$
B
$$38 + {1 \over {{2^{20}}}}$$
C
$$39 + {1 \over {{2^{20}}}}$$
D
$$39 + {1 \over {{2^{19}}}}$$
2
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
Let $${1 \over {{x_1}}},{1 \over {{x_2}}},...,{1 \over {{x_n}}}\,\,$$ (xi $$\ne$$ 0 for i = 1, 2, ..., n) be in A.P. such that x1=4 and x21 = 20. If n is the least positive integer for which $${x_n} > 50,$$ then $$\sum\limits_{i = 1}^n {\left( {{1 \over {{x_i}}}} \right)}$$ is equal to :
A
$${1 \over 8}$$
B
3
C
$${{13} \over 8}$$
D
$${{13} \over 4}$$
3
JEE Main 2018 (Offline)
+4
-1
Let A be the sum of the first 20 terms and B be the sum of the first 40 terms of the series
12 + 2.22 + 32 + 2.42 + 52 + 2.62 ...........
If B - 2A = 100$$\lambda$$, then $$\lambda$$ is equal to
A
496
B
232
C
248
D
464
4
JEE Main 2018 (Offline)
+4
-1
Let $${a_1}$$, $${a_2}$$, $${a_3}$$, ......... ,$${a_{49}}$$ be in A.P. such that

$$\sum\limits_{k = 0}^{12} {{a_{4k + 1}}} = 416$$ and $${a_9} + {a_{43}} = 66$$.

$$a_1^2 + a_2^2 + ....... + a_{17}^2 = 140m$$, then m is equal to
A
33
B
66
C
68
D
34
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