1
JEE Main 2019 (Online) 10th April Morning Slot
+4
-1
If for some x $$\in$$ R, the frequency distribution of the marks obtained by 20 students in a test is :

Marks 2 3 5 7
Frequency (x + 1)2 2x - 5 x2 - 3x x

then the mean of the marks is
A
3.0
B
2.8
C
2.5
D
3.2
2
JEE Main 2019 (Online) 9th April Evening Slot
+4
-1
The mean and the median of the following ten numbers in increasing order 10, 22, 26, 29, 34, x, 42, 67, 70, y are 42 and 35 respectively, then $${y \over x}$$ is equal to
A
$${7 \over 2}$$
B
$${8 \over 3}$$
C
$${9 \over 4}$$
D
$${7 \over 3}$$
3
JEE Main 2019 (Online) 9th April Morning Slot
+4
-1
If the standard deviation of the numbers –1, 0, 1, k is $$\sqrt 5$$ where k > 0, then k is equal to
A
2$$\sqrt 6$$
B
$$\sqrt 6$$
C
$$2\sqrt {{{5} \over 6}}$$
D
$$2\sqrt {{{10} \over 3}}$$
4
JEE Main 2019 (Online) 8th April Evening Slot
+4
-1
A student scores the following marks in five tests :

45, 54, 41, 57, 43.

His score is not known for the sixth test. If the mean score is 48 in the six tests, then the standard deviation of the marks in six tests is
A
$$100 \over {\sqrt 3}$$
B
$$10 \over {\sqrt 3}$$
C
$$10 \over3$$
D
$$100 \over3$$
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