If for a distribution of 20 items, $\sum(x-4)=10$ and $\sum(x-4)^2=85$ then the standard deviation is:
4
4.25
1.41
2
The odds against Arjun solving a problem are $\mathbf{5 : 2}$ and the odds in favour of Bhavana solving the same problem are 3:4. What is the probability that the problem is NOT solved by either of them?
$\frac{10}{49}$
$\frac{29}{49}$
$\frac{20}{49}$
$\frac{15}{49}$
If $\mathbf{3 ~ c m} / \mathbf{s}$ is the rate at which the side of an equilateral triangle increases, then the rate of change of area, when the side is $\mathbf{1 2 ~ c m}$ is:
$9 \sqrt{3} \mathrm{~cm}^2 / \mathrm{s}$
$18 \mathrm{~cm}^2 / \mathrm{s}$
$6 \sqrt{3} \mathrm{~cm}^2 / \mathrm{s}$
$18 \sqrt{3} \mathrm{~cm}^2 / \mathrm{s}$
If $\sin A+\sin 2 A=x$ and $\cos A+\cos 2 A=y$ then the value of the expression $\left(x^2+y^2\right)\left(x^2+y^2-3\right)$ equals
0
$3 y$
$\frac{y}{2}$
$2 y$
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