The value of (3)/(2) x (1)/(2) / (3)/(2) ; 20) An aeroplane covers a distance of 300 Km in 5 hrs.

To divide by a fraction, multiply by its reciprocal.

$$\frac{3}{4} \div \frac{3}{2} = \frac{3}{4} \times \frac{2}{3}$$

$$\frac{6}{12} = \frac{1}{2}$$

The options provided are A. 1, B. #, C. 100, D. 11, E. 12. None of the options match the calculated value of $\frac{1}{2}$.

The value is $\boxed{\frac{1}{2}}$.

20) An aeroplane covers a distance of 300 Km in 5 hrs.

$$\text{Distance} = 300 \text{ Km}$$ $$\text{Time} = 5 \text{ hrs}$$ $$\text{Average Speed} = \frac{300 \text{ Km}}{5 \text{ hrs}}$$

$$\text{Average Speed} = 60 \text{ Km/h}$$

Comparing this to the given options:
A. 35 Km/h
B. 40 Km/h
C. 50 Km/h
D. 60 Km/h
E. 65 Km/h

The calculated average speed matches option D.

The average speed of the aeroplane is $\boxed{\text{D. } 60 \text{ Km/h}}$.