$A$ $100 \text{ W}$ electric bulb is lighted for $2 \text{ hours}$ daily,and four $40 \text{ W}$ bulbs are lighted for $4 \text{ hours}$ everyday. Calculate the energy consumed (in $\text{kWh}$) in $30 \text{ days}$.

(25.2 KWH) Energy consumed by one $100 \text{ W}$ bulb working for $2 \text{ hours}$ daily:
$= \frac{100 \text{ W}}{1000} \times 2 \text{ h} = 0.2 \text{ kWh}$
Energy consumed by four $40 \text{ W}$ bulbs working for $4 \text{ hours}$ daily:
$= \frac{4 \times 40 \text{ W}}{1000} \times 4 \text{ h} = 0.64 \text{ kWh}$
Total energy consumed everyday:
$= 0.2 \text{ kWh} + 0.64 \text{ kWh} = 0.84 \text{ kWh}$
Total energy consumed in $30 \text{ days}$:
$= 0.84 \text{ kWh} \times 30 = 25.2 \text{ kWh}$