Page 135 - Start Up Mathematics_7

Solution: (a) C.P. of scooter = ` 12,000

S.P. of scooter = ` 10,000
 S.P. < C.P. ∴ The transaction results in a loss.
Loss = C.P. – S.P. = ` 12,000 – ` 10,000 = ` 2,000

Profit 2,000 2
Loss % = × 100 = × 100 = 16 %
C.P. 12,000 3
(b) C.P. of laptop = ` 25,000

S.P. of laptop = ` 15,000
 S.P. < C.P. ∴ The transaction results in a loss.
Loss = C.P. – S.P. = ` 25,000 – ` 15,000 = ` 10,000

Loss 10,000 2
Loss % = × 100 = × 100 = × 100 = 40%
C.P. 25,000 5
Example 20: I buy a TV for ` 10,000 and sell it at a profit of 12%. How much money do I get for
it?
Solution: C.P. of TV = ` 10,000
Profit % = 12%

∴ Profit = 12% of ` 10,000 = 12 × 10,000 = ` 1,200
100
∴ S.P. of TV = C.P. + Profit = ` 10,000 + ` 1,200 = ` 11,200

Example 21: Surbhi sells a scooty for ` 11,900. She loses 15% in the bargain. What was the price
at which she bought it?
Solution: Let the C.P. of scooty be P.
Loss percent = 15%
15
∴ Loss = 15% of P = 100 × P = 3P
20
We know, C.P. – Loss = S.P.

3P
⇒ P – 20 = ` 11,900
17P
⇒ = ` 11,900
20
11,900 × 20
⇒ P = ` = ` 700 × 20 = ` 14,000
17

Simple interest
You must have heard about the various loans offered by banks and other financial institutions for
our different needs like education, buying a house, vehicles, etc. The term loan refers to a sum
of money lent at interest. Just like a shopkeeper makes profit by selling an item at a price higher
than that at which he bought it, similarly these banks and finance companies also make money by
lending the money at interest. Let’s understand some related terms.
(i) Principal: The money lent or borrowed is called the principal or sum.
(ii) Interest: The additional money paid by the borrower over principal is called interest. It is
of two types—simple and compound.

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