Question

Match the columns.

Column 1	Column 2
Straight angle	Less than one-fourth of a revolution.
Right angle	More than half a revolution
Acute angle	Half of a revolution
Obtuse angle	One-fourth of a revolution
Reflex angle	Between $\frac{1}{4}$ and $\frac{1}{2}$ of a revolution

Answer 1

Explanation for $\left(\mathrm{A}\right)$:

Define straight angle.

A straight angle means an angle made by a straight line, i.e. $180°$

Hence, a straight angle needs half of a revolution.

Therefore $\left(\mathrm{A}\right)\to \left(\mathrm{iii}\right)$

Explanation for $\left(\mathrm{B}\right)$:

Define right angle.

Right angle is equal to $90°$

Hence, a right angle needs one-fourth of a revolution.

Therefore $\left(\mathrm{B}\right)\to \left(\mathrm{iv}\right)$

Explanation for $\left(\mathrm{C}\right)$:

Define acute angle.

Acute angle is an angle that measures between $90°$ and $0°$.

Hence, an acute angle needs less than one-fourth of a revolution.

Therefore $\left(\mathrm{C}\right)\to \left(\mathrm{i}\right)$

Explanation for $\left(\mathrm{D}\right)$:

Define obtuse angle.

Obtuse angle is an angle that measures between $90°$ and $180°$.

Hence, an obtuse angle needs a revolution between $\frac{1}{4}$ and $\frac{1}{2}$.

Therefore $\left(\mathrm{D}\right)\to \left(\mathrm{v}\right)$

Explanation for $\left(\mathrm{E}\right)$:

Define reflex angle.

Reflex angle is an angle that measures more than $180°$.

Hence, reflex angle needs more half of a revolution.

Therefore $\left(\mathrm{E}\right)\to \left(\mathrm{ii}\right)$.

Hence $\left(\mathrm{A}\right)\to \left(\mathrm{iii}\right)$, $\left(\mathrm{B}\right)\to \left(\mathrm{iv}\right)$,$\left(\mathrm{C}\right)\to \left(\mathrm{i}\right)$,$\left(\mathrm{D}\right)\to \left(\mathrm{v}\right)$,$\left(\mathrm{E}\right)\to \left(\mathrm{ii}\right)$.