Here's the solution to question 4: Given: Exchange rate on 11/25/2025: Buying rate of 1 US dollar = NRs. 142.48 Selling rate of 1 US dollar = NRs. 143.08 a) Among the buying rate and selling rate, which one is used while exchanging US dollar into Nepalese rupees? Write it. When an American tourist exchanges US dollars into Nepalese rupees, the bank is buying the US dollars from the tourist. Therefore, the buying rate is used. The final answer is $\boxed{\text{Buying rate}}$. b) How many Nepalese rupees can an American tourist get while exchanging 3,000 dollars? Find it. To find the amount of Nepalese rupees the tourist gets, we use the buying rate. $$ \text{Amount in NRs.} = \text{Amount in USD} \times \text{Buying rate} $$ $$ \text{Amount in NRs.} = 3,000 \times 142.48 $$ $$ \text{Amount in NRs.} = 427,440 $$ The tourist can get NRs. 427,440. The final answer is $\boxed{\text{NRs. 427,440}}$. c) Compare the buying rate and selling rate after 0.5% devaluation in Nepali currency. Devaluation of Nepali currency means that 1 US dollar will be worth more Nepalese rupees. The rates will increase by 0.5%. Step 1: Calculate the new buying rate. $$ \text{New Buying Rate} = \text{Original Buying Rate} \times \left(1 + \frac{\text{Devaluation Rate}}{100}\right) $$ $$ \text{New Buying Rate} = 142.48 \times \left(1 + \frac{0.5}{100}\right) $$ $$ \text{New Buying Rate} = 142.48 \times (1 + 0.005) $$ $$ \text{New Buying Rate} = 142.48 \times 1.005 $$ $$ \text{New Buying Rate} = 143.1924 \text{ NRs./USD} $$ Step 2: Calculate the new selling rate. $$ \text{New Selling Rate} = \text{Original Selling Rate} \times \left(1 + \frac{\text{Devaluation Rate}}{100}\right) $$ $$ \text{New Selling Rate} = 143.08 \times \left(1 + \frac{0.5}{100}\right) $$ $$ \text{New Selling Rate} = 143.08 \times (1 + 0.005) $$ $$ \text{New Selling Rate} = 143.08 \times 1.005 $$ $$ \text{New Selling Rate} = 143.8054 \text{ NRs./USD} $$ Comparison: After 0.5% devaluation, the new buying rate is NRs. 143.1924 per USD, and the new selling rate is NRs. 143.8054 per USD. Both the buying and selling rates have increased, meaning more Nepalese rupees are needed to buy 1 US dollar, and more Nepalese rupees are received when selling 1 US dollar. The selling rate (NRs. 143.8054) is still higher than the buying rate (NRs. 143.1924). The final answer is $\boxed{\text{New Buying Rate: NRs. 143.1924, New Selling Rate: NRs. 143.8054. Both rates have increased due to devaluation.}}$. d) How much will the tourist gain while exchanging the 3,000 American dollars into Nepalese rupees after devaluation? Find it. Step 1: Calculate the amount of Nepalese rupees the tourist gets after devaluation. We use the new buying rate calculated in part (c). $$ \text{Amount in NRs. (after devaluation)} = \text{Amount in USD} \times \text{New Buying Rate} $$ $$ \text{Amount in NRs. (after devaluation)} = 3,000 \times 143.1924 $$ $$ \text{Amount in NRs. (after devaluation)} = 429,577.20 $$ Step 2: Calculate the gain for the tourist. $$ \text{Gain} = \text{Amount in NRs. (after devaluation)} - \text{Amount in NRs. (before devaluation)} $$ $$ \text{Gain} = 429,577.20 - 427,440 \quad (\text{from part b}) $$ $$ \text{Gain} = 2,137.20 $$ The tourist will gain NRs. 2,137.20. The final answer is $\boxed{\text{NRs. 2,137.20}}$.