How many degrees are there in :

(i) two right angles

(ii) $\dfrac{1}{6}$ right angle

(iii) $1\dfrac{1}{2}$ right angles

(iv) a straight angle

(v) $\dfrac{2}{5}$ straight angle

(i) two right angles

One right angle = 90°

∴ Two right angles = 2 x 90° = 180°

Hence, the answer is 180°.

(ii) $\dfrac{1}{6}$ right angle

Right angle = 90°

∴ $\dfrac{1}{6}$ right angle = $\dfrac{1}{6} \times 90^{\circ}$ = 15°

Hence, the answer is 15°.

(iii) $1\dfrac{1}{2}$ right angles

Let's convert mixed to improper fraction:

$1\dfrac{1}{2} = \dfrac{3}{2}$

Right angle = 90°

∴ $\dfrac{3}{2}$ right angles = $\dfrac{3}{2} \times 90^{\circ}$

= $\dfrac{3}{1} \times 45^{\circ}$

= 135°

Hence, the answer is 135°.

(iv) a straight angle

A straight angle is always 180°.

Hence, the answer is 180°.

(v) $\dfrac{2}{5}$ straight angle

Straight angle = 180°

∴ $\dfrac{2}{5}$ straight angle = $\dfrac{2}{5} \times 180^{\circ}$

= $\dfrac{2}{1} \times 36^{\circ}$

= 72°

Hence, the answer is 72°.