#### Subject:

mathematics

#### Class:

class VII

#### Key Concepts

profit, loss, cost price, selling price, principal, interest, amount, rate, simple interest

#### essential questions

1. What is simple interest? How do we use it in everyday life?

2. What do various variables represent?

3. How can I use percent's to calculate simple interest?

4. What is profit and loss and how do we use it in real life?

#### Remembering:

**Profit and Loss**

- Fill in the blanks: i) Loss= (CP)- (SP) ii) CP= 100 * SP / (___+___) iii) Profit or loss is always reckoned on____ iv) 100/(100- loss%) * SP = ____
- Find the gain or loss percent: a) CP = Rs 2400 and SP= Rs 2592 b) CP= Rs 1650 and SP= Rs 1452 c) CP= Rs 12000 and SP=Rs 12800
- Find: a) SP= Rs 924 and Gain= 10% b) SP=Rs 1755 and Gain= 12.5%

**Simple Interest**

Find the simple interest and the amount when:

a) principal = Rs 6400, Rate=6% per annum and Time=2 years

b) Principal = Rs 2650, Rate = 8% per annum and Time = 2.5 years

c) Principal= Rs 1500, Rate = 12% per annum and Time= 3 years and 3 months

d) Principal= Rs 5000, Rate = 9%per annum and Time= 146 days

Find time when:

a) Principal= Rs 6400, Simple Interest= Rs 1152, Rate = 6% per annum

b)Principal= Rs 9540, Simple Interest= Rs 1908, Rate = 8% per annum

c) Principal= Rs 5000, Simple Interest= Rs 6450, Rate = 12% per annum

#### understanding:

**Profit and Loss**

- A man buys an article for Rs 27.50 and sells it for Rs 28.60. Find his gain percent. a) 1 % b) 2 % c) 3 % d) 4%
- In terms of percentage profit, which among following the best transaction: a) CP Rs 36, Profit Rs 17 b) CP Rs 50, Profit Rs 24 c) CP Rs 40, Profit Rs 19 d) CP Rs 60 Profit 29
- A book was sold for Rs 27.50 with a profit of 10%. If it were sold for Rs 25.75 then what would have been percentage of profit or loss?
- Ali buys an old scooter Rs 4700 and spends Rs 800 on its repairs. If he sells it for Rs 5800 what is his gain percent will be?
- An article was bought for Rs 400 and sold for Rs 336. Find his loss or profit percent.

**Simple Interest**

- Sam borrowed some money from his friend at simple interest of 6% per annum. He returned his friend Rs 15600. After how much time did Sam return the money if he borrowed Rs 12000?
- Kabir paid Rs 9600 as interest on a loan he took 5 years ago at 16 % rate of simple interest. What was the amount he took as loan?
- Guddi invested some money in a bank at rate of 6% per annum. At Simple Interest after 9 years, she got Rs 8470. How much did she invest?
- The simple interest on a certain sum for 3 years at 10% per annum is Rs 829.50. Find the sum.
- At what rate percent per annum will Rs 3600 amount to Rs 4734 in 3.5 years?
- In what time will Rs 5600 amount to Rs 6720 at 8% per annum?

#### Application:

**Profit and Loss**

- If a person sells a sari for rs 5200 making a profit of 30%, then the cost price of the sari will be: a) Rs 4420 b) Rs 4000 c) Rs 3900 d) Rs 3800
- A person sold a stove for Rs 423 and incurred a loss of 6%. At what price would it be sold so as to earn a profit of 8%? a) 525 b) 500 c) 490 d) 486
- A fruit seller buys lemon at 2 for a rupee and sells then at 5 for three rupees. What is his gain percent? a) 10% b) 15% c) 20% d) 25%
- A sells a car to B at 10% loss. If B sells it for Rs 54000 and gains 20%. The cost price of the car for A was: a) Rs 25000 b) Rs 50000 c) Rs 37500 d) Rs 60,000
- Ramesh sold a statue for a price 25% higher that the original price of the statue. He had however bought the statute at 20% discount on the original price. With the profit of Rs 2025, find the original price of the statue. a) Rs 6000 b) Rs 7500 c) Rs 3500 d) Rs 4500
- A person incurs a loss of 5% by selling a watch for Rs 1140. At what price should the watch be sold to earn 5% profit: a) Rs 1200 b) Rs 1230 c) Rs 1260 d) Rs 1290
- If the cost price of 15 pens is equal to the selling price of 20 pens. Find the loss percent.

**Simple Interest**

- Suresh for 2 years invested Rs 500 in SBI. he also invested Rs 300 in a bank for 4 years. At the end he received Rs 220 from both banks as simple interest. What must have been rate of interest?
- In how much time would the simple interest on a certain sum be 0.125 times the principal at 10% per annum?
- Raman paid Rs 11400 as interest after 9 years. he had borrowed some money at the rate of 6% for first 2 years, 9% for next 3 years and 14% for rest f the period. How much money did he borrow?
- Ram gets Rs 2600 for Rs 2000 in 5 years at some rate of simple interest. Had he invested in other places where rate of simple interest is 3% more than current rate, how much would have Ram got in same time?

#### Analysis:

**Profit and Loss**

- If selling price of 40 articles is equal to cost price of 50 articles, the loss or gain percent will be: a) 25% loss b) 20% loss c) 25% gain d) 20% gain
- The ratio of cost price and selling price is 4:5. What is the profit percent. a) 10% b) 20% c) 25% d) 30%

**Simple Interest**

- A sum of money becomes 8/5 of itself in 5 years at certain rate of simple interest. Find the rate of interest.
- Aman got salary of rs 8600. the salary was divided into two parts and invested. Find the difference between the two parts of his salary if in the first part he got simple interest at 15% per annum in 4 years, which was same as the second part which he invested at 20% for 3years.