JEE MAIN - Mathematics (2020 - 9th January Evening Slot)
1
If 10 different balls are to be placed in 4 distinct
boxes at random, then the probability that two
of these boxes contain exactly 2 and 3 balls is :
Answer
(D)
$${{945} \over {{2^{10}}}}$$
2
The number of terms common to the two A.P.'s
3, 7, 11, ....., 407 and 2, 9, 16, ....., 709 is ______.
Answer
14
3
In the expansion of $${\left( {{x \over {\cos \theta }} + {1 \over {x\sin \theta }}} \right)^{16}}$$, if $${\ell _1}$$ is
the least value of the term independent of x
when $${\pi \over 8} \le \theta \le {\pi \over 4}$$ and $${\ell _2}$$ is the least value of the
term independent of x when $${\pi \over {16}} \le \theta \le {\pi \over 8}$$, then
the ratio $${\ell _2}$$ : $${\ell _1}$$ is equal to :
Let $$\overrightarrow a $$, $$\overrightarrow b $$ and $$\overrightarrow c $$ be three vectors such that $$\left| {\overrightarrow a } \right| = \sqrt 3 $$,
$$\left| {\overrightarrow b } \right| = 5,\overrightarrow b .\overrightarrow c = 10$$ and the angle between $$\overrightarrow b $$ and $$\overrightarrow c $$
is $${\pi \over 3}$$. If $${\overrightarrow a }$$ is perpendicular to the vector $$\overrightarrow b \times \overrightarrow c $$ , then $$\left| {\overrightarrow a \times \left( {\overrightarrow b \times \overrightarrow c } \right)} \right|$$ is equal to _____.
Answer
30
10
If A = {x $$ \in $$ R : |x| < 2} and B = {x $$ \in $$ R : |x – 2| $$ \ge $$ 3};
then :
Then the area
(in sq. units) of the region bounded by the
curves, y = ƒ(x) and y = g(x) between the lines,
2x = 1 and 2x = $$\sqrt 3 $$, is :
Answer
(D)
$${{\sqrt 3 } \over 4} - {1 \over 3}$$
13
If $$x = 2\sin \theta - \sin 2\theta $$ and $$y = 2\cos \theta - \cos 2\theta $$,
$$\theta \in \left[ {0,2\pi } \right]$$, then $${{{d^2}y} \over {d{x^2}}}$$ at $$\theta $$ = $$\pi $$ is :
Answer
(A)
$${3 \over 8}$$
14
A random variable X has the following
probability distribution :
X:
1
2
3
4
5
P(X):
K2
2K
K
2K
5K2
Then P(X > 2) is equal to :
Answer
(D)
$${23 \over {36}}$$
15
Let a, b $$ \in $$ R, a $$ \ne $$ 0 be such that the equation,
ax2 – 2bx + 5 = 0 has a repeated root $$\alpha $$, which
is also a root of the equation, x2 – 2bx – 10 = 0.
If $$\beta $$ is the other root of this equation, then
$$\alpha $$2 + $$\beta $$2 is equal to :
Answer
(D)
25
16
The following system of linear equations
7x + 6y – 2z = 0
3x + 4y + 2z = 0
x – 2y – 6z = 0, has
Answer
(C)
infinitely many solutions, (x, y, z) satisfying
x = 2z
17
Let [t] denote the greatest integer $$ \le $$ t
and $$\mathop {\lim }\limits_{x \to 0} x\left[ {{4 \over x}} \right] = A$$. Then the function,
f(x) = [x2]sin($$\pi $$x) is discontinuous, when x is
equal to :
Answer
(A)
$$\sqrt {A + 1} $$
18
If the curves, x2 – 6x + y2 + 8 = 0 and
x2 – 8y + y2 + 16 – k = 0, (k > 0) touch each other
at a point, then the largest value of k is ______.
Answer
36
19
Let ƒ and g be differentiable functions on R
such that fog is the identity function. If for some
a, b $$ \in $$ R, g'(a) = 5 and g(a) = b, then ƒ'(b) is
equal to :
Answer
(D)
$${1 \over 5}$$
20
Let an be the nth term of a G.P. of positive terms.