Page 112 - ICSE Math 8

Example 2: If the cost price of 14 apples is the same as the selling price of 12 apples, find the gain or loss
per cent.
Solution: Let the C.P. of each apple be ` 1. Then, C.P. of 12 apples = ` 12
C.P. of 14 apples = ` 14 = S.P. of 12 apples
∴ S.P. of 12 apples = ` 14
Since S.P. of 12 apples > C.P. of 12 apples, there is a gain.

Gain = ` (14 – 12) = ` 2
Ê Gain ˆ Ê 2 ˆ
Gain% = Á C.P. ¥100 % = Á ¥100 % = 16.66% = 16.7% (approx)
˜
˜
Ë
¯
¯
Ë12
Hence, Gain% = 16.7%
Try These
1. By selling a television set for ` 4,500, a dealer suffers a loss of 10%. Find the cost price of
the television.
2. A shopkeeper bought 15 transformers for ` 450 each. He spent ` 30 as the transportation
charges and ` 12 per transformer on packaging. He sold them at the rate of ` 520 per
transformer. Find his profit or loss per cent.

Example 3: A shopkeeper bought 100 bed covers for ` 2,000 each. Due to some calculation mistake, he
sold 10 bed covers at ` 1,200 each. At what rate should he sell the remaining, so as to have a
profit of 14% on the whole?
Solution: C.P. of 1 bed cover = ` 2,000
∴ C.P. of 100 bed covers = ` (100 × 2,000) = ` 2,00,000

Desired profit% = 14%
Ê 14 ˆ
∴ Desired profit = 14% of 2,00,000 = ` Á 100 ¥ 200 000, , ˜ ¯ = ` 28,000
Ë
∴ S.P. of 100 bed covers = ` (2,00,000 + 28,000) = ` 2,28,000

By mistake 10 bed covers were sold for ` 1,200 each.
∴ S.P. of these 10 bed covers = ` (10 × 1,200) = ` 12,000
Hence, desired S.P. of remaining (100 – 10) 90 bed covers
= ` (2,28,000 – 12,000) = ` 2,16,000
216 000,,
∴ S.P. of 1 bed cover = ` = ` 2,400
90
The shopkeeper should sell the remaining 90 bed covers for ` 2,400 each.

Example 4: A CD player was sold at a profit of 10%. Had it been sold for ` 25 more, the profit would have
been 12%. Find the cost price of the CD player.
Solution: Let the C.P. of CD player be ` x.
Profit% = 10%
10 x
∴ Profit = 10% of x = ` x = `
100 10

Ê x ˆ 11x
⇒ S.P. = C.P. + Profit = ` x + 10 ˜ = ` 10
Á
Ë
¯
New profit% = 12%
100