Back to: MATHEMATICS JSS 2
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In today’s Mathematics class, We will be discussing “Simple Interest. We will so be looking at Profit and Loss. We will ten round up with Discount and Commision. We hope you enjoy the class!
SIMPLE INTEREST
Interest is the money paid for saving a particular amount of money.
Simple interest can be calculated using the formula
$SimpleInterestI=\frac{PRT}{100}$
Where P= principal, R=rate & T= time
Also total amount =principal +interest
Example 1
Find the simple interest on N60, 000 for 5 years at 9% per annum
Solution
Applying
$I=\frac{PRT}{100}$
where P= N 60,000 R=9% T=5 years
$I=\frac{60,000\times 9\times 5}{100}\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}=N27,000$
Example 2
A man borrows N 1,600,000 to buy a house. He is charged interest at the rate of 11% per annum. In the first year, he paid the interest on the loan. He also paid back N 100,000 of the money borrowed. How much did he pay back altogether? If he paid this money by monthly instalment, how much did he pay per month?
Solution
P= N 1,600,000 R=11% T=1 year
Interest on N 1,600,000
$I=\frac{PRT}{100}=\frac{1,600,000\times 11\times 1}{100}=N176,000$
The total amount paid in the first year= N 100,000 + N 176,000 = N 276,000
Monthly payment =
$\frac{276,000}{12}$
= N 23,000
Classwork
 Find the simple interest on the following:
 N 10,000 for 31/2 years at 4% per annum
 N 20,000 for 4 years at 4% per annum
 A man got N 1,800,000 loan to buy a house. He paid interest at a rate of 9% per annum. In the first year, he paid the interest on the loan. He also paid back N 140,000 of the money he borrowed. (a) How much did he pay in the first year altogether?
Profit and loss percent
Profit means to gain, while loss is the inverse of profit.
% Profit is the percentage of the gain made from a particular product or item
$\%Profit=\frac{profit}{Costprice}$
To find the selling price of an article
At loss, Selling price = cost price – loss
At gain, Selling = cost price + profit
Example
 A trader buys a kettle for N 800 and sells at a profit of 15%. Find the actual profit and the selling price
Solution
Profit =15 of N 800
=15 x800
= N 120
Selling price = C. + profit
= 800+120
= N 920
 A hat is bought for N 250 and sold for N 220, what is the loss percentage
Solution
Cost price C.P = N 250
Selling price = N 220
Lost= N 250 N 220 = N 30
% Loss =
$\%Loss=\frac{loss}{C.P}\times 100\%$
$=\frac{30}{250}\times 100\%\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}=\frac{3}{25}\times 100=12\%\phantom{\rule{0ex}{0ex}}$
Classwork
 Find the actual profit and the selling price of a material which cost #1000 sold at a profit of 15%
 A farmer buys a piece of land for #40,000 and sells it for N 33,000 what is the percentage loss?
 A car that cost N 336,000 was sold at a loss of 17½%. What is the selling price
Discount and Commission
A discount is a reduction in the price of goods or items. Discounts are often given for paying in cash.
Commission: this is a payment or reward for selling an item.
Examples
 Find the discount price, if a discount of 25% is given on a market price of #9,200
Solution
Discount =25% of N 9,200
$=\frac{25}{100}\times 9,200=2,300$
 A radio cost N 5,400. A 12½% discount is given for cash. What is the cash price
Solution
Discount =12 ½% of N 5,400
$=\frac{25}{2}\times 100\times 5400\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}=25\times 500\times 5400=675\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}Cashprice=N5,400\u2013675=N4725$
 A bank charges 2½ % commission for issuing a bank draft to its customers, if a customer obtained a bank draft for N 84,000 from the bank, calculates the total cost of the bank draft.
Solution
Commission =22% of N 84,000
5/2/100 x 84,000
=5/2×100 x84, 000
= N 2,100
Total cost of bank draft = 84,000+ N 2,000 = N 86,100
Classwork
 Find the discount price if a discount of 20% is given on a market of N 2,915
 The selling price of a table is N 14,000, the trader gives a 25% discount for cash, what is the cash price
 An insurance agent sells N 284,000 worth of insurance, his commission is 20%. How much money does he get?
READING ASSIGNMENT
New General Mathematics, UBE Edition, Chapter 1, pages 7879
Essential Mathematics by A J S Oluwasanmi, Chapter 1, pages 6164
WEEKEND ASSIGNMENT
 Calculate the simple interest on N 200 in 2 years at 4% per annum (a) N 160n (b) N 240 (c) N 16 (d) N 260
 Calculate the simple interest on N 20,000 for 2^{1/2 }years at 2% per annum (a) N 10 (b) N10, 000 (c) N 1000 (d) N 2000
 Find the simple interest on N 40,000 for 1 year at 5% per annum (a) N 100 (b) N 250 (c) N 2,590 (d) N 50
 What is the simple interest on #70,000 for 1 year at 4% per annum (a) N 2,800 (b) N 2,000 (c) N 2,400 (d) N 2,300
 Find the simple interest on N 10,000 for 3 years at 6% per annum (a) N 1,800 (b) N 1000 (c) N1,850 (d) N 1,200
THEORY
 Find the simple interest on the following

 N 55,000 for 4 years at 60% per annum
 N 25,000 for 3 years at 5% per annum
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In our next class, we will be talking about Approximation of Numbers. We are very much eager to meet you there.
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