A scientific calculator is available at Universal shop in Hazratganj at 20% discount and the same is available at only 15% discount at Bhootnath market. Pooja has just sufficient amount of Rs 800 to purchase it at Universal shop, Hazratganz. What is the amount that Pooja has less than the required amount to purchase it at Bhootnath?
(a) Rs. 70
(b) Rs. 50
(c) Rs.100
(d) Data Insufficient

Hint: First, before proceeding for this, we must suppose the value of the calculator before discount at Universal shop be x. Then, we get the expression as x-20% of x=800 and by solving it we get the accrual price of the calculator. Then, we are given the question that the same price is marked on the calculator in Bhootnath market but with the less discount of 15% and by using it we get the difference in the amount of calculator at Bhootnath market and Universal shop, Hazratganz.

Complete step-by-step answer:
In this question, we are supposed to find the amount hat Pooja has less than the required amount to purchase it at Bhootnath when a scientific calculator is available at Universal shop in Hazratganj at 20% discount and the same is available at only 15% discount at Bhootnath market and Pooja has just sufficient amount of Rs 800 to purchase it at Universal shop, Hazratganz
So, before proceeding for this, we must suppose the value of the calculator before discount at Universal shop be x.
Then, we know after giving 20% discount on the calculator, she bought the calculator at Rs. 800.
So, we get the expression from the above condition as:
x-20% of x=800
Then, by solving the above expression, we get the actual value of calculator at Universal shop as:
$\begin{align}
  & x-\dfrac{20}{100}\times x=800 \\
 & \Rightarrow \dfrac{100x-20x}{100}=800 \\
 & \Rightarrow \dfrac{80x}{100}=800 \\
 & \Rightarrow x=\dfrac{800\times 100}{80} \\
 & \Rightarrow x=1000 \\
\end{align}$
So, we get the actual value of the calculator before discount at Universal shop as Rs. 1000.
Now, we are given the question that the same price is marked on the calculator in Bhootnath market but with the less discount of 15%.
Now, we need to calculate the discount on calculator at Bhootnath market is given by:
15% of 1000
So, by solving we get the value of discount as:
$\dfrac{15}{100}\times 1000=150$
Now, we get the value of selling price of calculator at Bhootnath market as:
$1000-150=850$
So, Pooja needs to spend Rs 850 at Bhootnath market for the same calculator which she bought from Universal shop, Hazratganj at Rs. 800.
So, we need to find the amount that Pooja paid less to buy that calculator is given by:
$850-800=50$
So, we get the required answer as Rs 50.

So, the correct answer is “Option (b)”.

Note: Now, to solve these type of the questions we need to know some of the basics of the discount that is marked on the price by using the general formula as d% is the discount percent marked on price x and then the actual amount we need to pay is given by:
x-d% of x=$x-\dfrac{d}{100}\times x$