## Class 9 Mathematics Note

# HOME ARITHMETIC

**Home Arithmetic **

Home arithmetic deals with the financial activities based on the household purpose. Eg- telephone bill, electricity bill money exchange etc.

** Electricity Bill**

The consumption of the electricity by a household is measured in the number of units by the electric meter.

The number of units of electricity consumed is calculated as

Reading of the recent month – Reading of the previous month

**Telephone bill **

Telephone charge rate as per Nepal telecom

Cost of minimum 100 calls = Rs 250

Above 100 calls it costs Rs 1.50 per call

Scheme of payment

Call charge = minimum call charge + additional no of calls * additional call

Telecom service charge (TSC) =10%of call charge

Total amount = call charge + telecom service charge (TSC)+value added tax

**Money exchange **

Money exchange means to convert currency of a country into currency of another country. Money exchange has its importance in international trades and tourism.

**Examples**

1.

The charge of electricity is Rs 80 for the first 20 units and Rs 7.30 per unit from 21 units to 250 units and Rs 9.90 per units consumption of electricity.

a. Soln:

Total units = 160 units.

Now, Excessive number of units = 160 – 20 = 140 units.

Now, Cost of 140 units = 140 * Rs. 7.30

= Rs. 1,022.

Now, Total consumption of electricity = Rs. 1,022 + Rs. 80

= Rs. 1102.

2.

The minimum charge up to 100 calls is Rs 250.if charge for each additional call Is Rs 1.50. How much will be the charge for 420 calls with 10% TSC and 13% VAT.

Soln

Charge for 100 calls = Rs. 250

Now, additional calls = 420 – 100 = 320

So, cost of 320 calls = 320 * Rs. 1.50 = Rs. 480.

So, the total cost = Rs. 250 + Rs. 480 = Rs. 730

Now, Cost with 10% TSC = Rs. 730 + 10% of Rs. 730

= 730 + $\frac{{10}}{{100}}$ * 730

= Rs. 803.

Now, Cost with 13% VAT = Rs. 803 + 13% of 803

= Rs. 803 + 104.39

= Rs. 907.39.

3.

The amount of water bill of a household of the month Baiskh is Rs 220. Calculate the amount to be paid with a miscellaneous charge of Rs 5 if the payment is made on the first week of jestha receiving 3% rebate .

a. Soln:

Monthly Water Bill = Rs. 220

3% rebate = 3% of Rs. 220 = Rs. 6.60

Miscellaneous charge = Rs 5.

Total Bill = Monthly bill – 3% rebate + Miscellaneous charge = Rs. 220 – Rs. 6.60 + Rs. 5 = Rs. 218.4

4.

A man exchanged some dollars for Rs 35000 at the exchange rate of $1= Rs 70 .Next week , if nepali currency was devaluated by 10% what percent of profit wouldhe make again by exchanging dollars with Nepalicurrency .

. Soln:

1$ = Rs. 70

So, Rs. 1 = $\frac{1}{{70}}$ $

Or, Rs. 35,000 = $\frac{{35,000}}{{70}}$ $

Or, 35,000 = 500$.

Since, the Nepali currency was devaluated by 10%. So,

Or, 1$ = Rs. 70 + 10% of 70

= Rs.70 + 7

= Rs. 77.

So, 5000$ = 500$ * Rs. 77 = Rs. 38,500.

So, Now, Profit = Rs. 38,500 – Rs. 35,000

= Rs. 3,500.

Now, profit % = $\frac{{3,500}}{{35,000}}$ * 100% = 10%.

So, He had a profit of 10%.