$A$ bag $X$ contains $2$ white and $3$ black balls and another bag $Y$ contains $4$ white and $2$ black balls. One bag is selected at random and a ball is drawn from it. Then the probability for the ball chosen to be white is

Which one of the following characters is not typical of the class Mammalia?

The more commonly used baking powder contains about $30 \% NaHCO_3$,$20 \% NaAl(SO_4)_2$,$10 \% Ca(H_2PO_4)_2$ and $40 \% \text{starch}$. Which of the following statements is/are correct?

If the wavelength of an electromagnetic radiation is $2000 \ \mathring{A}$,what is its energy in ergs?

If $\overrightarrow{a} = 2\widehat{i} - \widehat{j} + \widehat{k}$,$\overrightarrow{b} = \widehat{i} + \widehat{j} - 2\widehat{k}$ and $\overrightarrow{c} = \widehat{i} + 3\widehat{j} - (\lambda^2 + 3\lambda)\widehat{k}$ (where $\lambda$ is a constant) and $\overrightarrow{a}$ is perpendicular to $\overrightarrow{c} - \lambda\overrightarrow{b}$,then the sum of different values of $\lambda$ is:

........ of a reaction cannot be determined experimentally.