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School SEE Compulsory Mathematics

Currency and Exchange Rate

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Currency is the official money of a country used for buying goods and services. When traveling or doing business abroad, Nepali Rupees must be exchanged for the foreign currency. The exchange rate is determined by the central bank, with a buying rate (bank buys foreign currency) and a selling rate (bank sells foreign currency). Selling rate is always higher than buying rate. Currency conversion can be done using Nepali Rupees as a bridge or by chain rule. Profit or loss occurs when the exchange rate changes during conversion.

1. Currency

Notes:

Currency is the official money of a country used for transactions.

Each country has its own currency (e.g., Nepal = Nepali Rupee, USA = Dollar, China = Yuan).

Nepali Rupees cannot be used directly abroad; foreign currency must be used.

People working abroad send money to Nepal, and their family receives it in Nepali Rupees, converted at the prevailing exchange rate.

Example Qn:
Q: Can a Nepali student buy goods in the USA using Nepali Rupees?
Solution: No. They must exchange Nepali Rupees for US Dollars to buy goods.

2. Exchange Rate

Notes:

Exchange Rate = value of one currency in terms of another.

Determined by: Central Bank of a country (Nepal Rastra Bank in Nepal).

Types of rates:

Buying rate: Rate at which bank buys foreign currency from people.

Selling rate: Rate at which bank sells foreign currency to people.

Selling rate is always higher than buying rate because banks earn profit from the difference.

Formula:

Selling rate−Buying rate=Bank’s profit per unit currency\text{Selling rate} - \text{Buying rate} = \text{Bank’s profit per unit currency}Selling rate−Buying rate=Bank’s profit per unit currency

Example Qn:
Q: $1 = Rs.127.50 (buying), $1 = Rs.128 (selling). How much profit does the bank earn on $500?
Solution:

Profit per $1 = 128 – 127.50 = 0.50

Profit on $500 = 0.50 × 500 = Rs. 250

3. Currency Conversion

Notes:

To convert currencies, we can use Nepali Rupees as a bridge or chain rule.

Chain Rule:

A→B→C  ⟹  A×B×C=B×C×AA \to B \to C \implies A \times B \times C = B \times C \times AA→B→C⟹A×B×C=B×C×A

Example: To convert Canadian Dollar (CAD) to Japanese Yen (JPY) using Nepali Rupees:

Example Qn:
Q: 1 CAD = Rs. 98.08, 10 JPY = Rs. 9.37. Find 1 CAD in JPY.
Solution:

1 CAD =98.08÷(9.37/10)=104.67 JPY1 \text{ CAD } = 98.08 \div (9.37/10) = 104.67 \text{ JPY}1 CAD =98.08÷(9.37/10)=104.67 JPY 

4. Profit and Loss in Currency Exchange

Notes:

When foreign currency is bought or sold, exchange rate fluctuations can cause profit or loss.

Profit: Nepali Rupee devalues after buying foreign currency.

Loss: Nepali Rupee inflates after buying foreign currency.

Example Qn:
Q: Exchange Rs. 8,40,000 into £ (1£ = Rs.150). After 5 days, Rs. devalues 5%. What is the loss?
Solution:

£ bought = 8,40,000 ÷ 150 = £5,600

New rate = 150 – 5% of 150 = Rs.142.50

Rs. received = 5,600 × 142.50 = Rs.7,98,000

Loss = 8,40,000 – 7,98,000 = Rs. 42,000

5. Import and Export

Notes:

Businesses dealing with international trade must convert currencies.

Selling price includes: cost + export tax + profit.

Currency conversion is needed to calculate selling price in foreign currency.

Example Qn:
Q: 900 Pasmina shawls cost Rs. 4,000 each. Export tax 5%, profit 20%, €1=Rs.130. Find total selling price in Euros.
Solution:

Total cost = 900 × 4000 = 36,00,000

After 5% tax = 36,00,000 + 1,80,000 = 37,80,000

Add 20% profit = 37,80,000 + 7,56,000 = 45,36,000

Convert to Euros = 45,36,000 ÷ 130 = €34,892.30

6. Key Formulas

Currency Conversion via Rupees:

Currency A=Value in NRsRate of A\text{Currency A} = \frac{\text{Value in NRs}}{\text{Rate of A}}Currency A=Rate of AValue in NRs​

Profit/Loss in currency exchange:

Profit/Loss=(Old Rate−New Rate)×Amount in Foreign Currency\text{Profit/Loss} = (\text{Old Rate} - \text{New Rate}) \times \text{Amount in Foreign Currency}Profit/Loss=(Old Rate−New Rate)×Amount in Foreign Currency

Chain Rule for currency conversion:

A→B→C:A×B×C=B×C×AA \to B \to C : A \times B \times C = B \times C \times AA→B→C:A×B×C=B×C×A 

7. Practice Questions with Solutions

Q: Rs. 85,500 exchanged into $ (1$ = Rs.126.35). How much $?
A: 85,500 ÷ 126.35 = $676.69

Q: Convert 250 AUD into Swiss Frank (1 AUD = Rs.87.82, 1 CHF = Rs.133.76).
A: 250 × 87.82 ÷ 133.76 = 164.14 CHF

Q: Sell Rs. 2,00,000 in Australian $ (1 AUD = Rs.88.23 selling).
A: 2,00,000 ÷ 88.23 = AUD 2266.80

Q: American $500 = £390, £50 = Rs.7,547. How many $ for Rs.10,308?
A: $87.55

Q: Salary in Australia: 37 AUD/hour, 5 hours/day, 6 days/week, Rs.90/AUD. Find weekly salary in NRs.
A: 37 × 5 × 6 = 1,110 AUD; 1,110 × 90 = Rs.99,900

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