Question

A mobile company charges Rs 1.5 per minute during the daytime (7 am to 11 pm) and Rs x per minute during night (11 pm to 7 am). The total talking time during night decreases by 50%. Find the value of x if the average amount charged by the mobile company during the whole day is Rs 1.40 per minute?

Answer 1

Let the talk time during daytime be $y$ minutes.

As the  total talking time during night decreases by 50% with respect to daytime.So,it will be half of that in daytime.

Talking time for 11 pm to 7 am will be $\frac{y}{2}$ minutes.

Total talking time$=y+\frac{y}{2}=\frac{3y}{2}$

As per the question,Total amount of charge during daytime $=y\times 1.5$

Total amount of charge during nighttime$=x\times \frac{y}{2}$

Average amount charged$=\frac{Total \ amount}{Total \ time}=\frac{y \times 1.5+x\times 0.5y}{1.5y}=1.40$

$\implies \frac{1.5+0.5x}{1.5}=1.40 \implies x=Rs\ 1.20/min$