A scientific calculator is Rs M at Universal Shoppe (Hazratganj) with 20% discount and Rs M at Universal Shoppe (Bhootnath) with 15% discount. Ms. Agrawal has exactly Rs 800 to buy at Hazratganj. How much less than required is she to buy at Bhootnath?

Introduction:
Equal MRPs at two stores, different discounts. If an amount exactly matches the discounted price at one store, we can recover the MRP and then compute the price (and shortfall) at the other store.

Given Data / Assumptions:

• At Hazratganj: price = 0.8 * M = Rs 800 ⇒ MRP M = Rs 1000
• At Bhootnath: price = 0.85 * M

Concept / Approach:
Compute the Bhootnath price using the recovered MRP and compare it with the amount available (Rs 800) to find the shortfall.

Step-by-Step Solution:
M = 800 / 0.8 = 1000Bhootnath price = 0.85 * 1000 = Rs 850Shortfall = 850 − 800 = Rs 50

Verification / Alternative check:
Reverse check: 20% discount on 1000 is 800 (fits the “just sufficient” statement).

Why Other Options Are Wrong:
70/100 are not consistent with 15% discount on Rs 1000; data is sufficient.

Common Pitfalls:
Assuming different MRPs; confusing percent of price with absolute rupees before solving for M.

Final Answer:
Rs. 50