21.

$\mathrm{If} \mathrm{x} = \frac{2}{3} \mathrm{and} \mathrm{y} = \frac{3}{4}, \mathrm{then} \mathrm{a} \mathrm{rational} \mathrm{number} \mathrm{between} {\left(\mathrm{x} - \mathrm{y}\right)}^{ - 1} \mathrm{and} \left({\mathrm{x}}^{ - 1} - {\mathrm{y}}^{ - 1}\right) \mathrm{is}$

• $\frac{2}{3}$

• $- \frac{71}{2}$

• $- \frac{71}{12}$

• $\frac{1}{6}$

$$\begin{gathered} \mathrm{If} 0.001 + 1.01 + 1.001 - (1.03 \mathrm{x} 0.1) ( 1 ) + (1.11 + 0.1) + \mathrm{x} \\ = 1.4 \mathrm{x} {\left(\frac{1}{10}\right)}^{ - 1}, \mathrm{then} \mathrm{the} \mathrm{value} \mathrm{of} \mathrm{the} \mathrm{x} \mathrm{is} \end{gathered}$$

• 0.919

• 0.785

• 0.758

• 0.991

$\mathrm{If} \frac{\sqrt{1058} \times \sqrt{648}}{\mathrm{x}} = 18, \mathrm{then} \mathrm{the} \mathrm{value} \mathrm{of} \mathrm{x} \mathrm{is}$

• 36

• 46

• 58

• 23

$$\begin{gathered} \mathrm{What} \mathrm{is} \mathrm{the} \mathrm{value} \mathrm{of} \mathrm{A} \mathrm{such} \mathrm{that} \\ \sqrt[3]{500} \times \sqrt[3]{ - 3456} = 40 \times \mathrm{A} \mathrm{is} \mathrm{true} ? \end{gathered}$$

•  - 3

•  - 12

• - 15

• - 2

One of the factors of x⁴ + 4 is

• x² + 2

• x² + 2x - 2

• x² - 2x + 2

• x² - 2

The mean of the five observations x, x + 2, x + 4, x + 6, x + 8 is 11. Then, the mean of the first three observations is

• 12

• 2

• 20

• 9

A bag has 5 red marbles, 4 green marbles and 3 blue marbles. All marbles are identical in all respects other than colour. A marble is taken out from the bag without looking into it. What is the probability that it is a non-green marble?

• $\frac{1}{3}$

• $\frac{2}{3}$

• $\frac{7}{12}$

• $\frac{5}{12}$

If AB x BA = BCB, where A, B and C stand for just one digit and $\mathrm{A} \ne \mathrm{B} \ne \mathrm{C}$, then the value of A + B + C

• 9

• 8

• 6

• 10

If x, y and z represent the number of faces, number of vertices and number of edges respectively of a polyhedra, then which of the following is true?

• x + 2 = z - y

• z - 2 = x - y

• y - 2 = z + x

• x - 2 = z - y

Ravi purchased two articles for t 1500 each. He sold them, gaining 6% on one and losing 4% on the other. His gain/loss per cent in the whole transaction is

• gain, 1%

• Loss, $1\frac{1}{2}\%$

• gain, 2%

• loss, 1%