Page 181 - Start Up Mathematics_8 (Non CCE)

Example 6: 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 = `
fi S.P. = C.P. + Profit 100 10

Ê x ˆ 11x
= ` x + 10 ˜ ¯ = ` 10
Á
Ë
New profit% = 12%
12x 3x
\ New profit = 12% of x = ` = `
100 25
Ê 3 xˆ 28 x
fi New S.P. = ` x + 25 ˜ ¯ = ` 25
Á
Ë
According to the question, the difference between new S.P. and original S.P. is ` 25.

28 11x
fi x – = 25
25 10
56x - 55x x
fi = 25 fi = 25 fi x = 50 × 25 = 1,250
50 50
Hence, the C.P. of CD player = ` 1,250
Example 7: 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 percent.
Solution: C.P. of 1 transformer = ` 450
\ C.P. of 15 transformers = ` (15 × 450) = ` 6,750

Transportation cost = ` 30
Amount spent on packaging = ` (12 × 15) = ` 180
\ Total overhead expenses = ` (30 + 180) = ` 210
Hence, total C.P. = ` 6,750 + ` 210 = ` 6,960

S.P. of 1 transformer = ` 520
\ S.P. of 15 transformers = ` (15 × 520) = ` 7,800
Since S.P. > C.P., there is a profit.
\ Profit = S.P. – C.P. = ` 7,800 – ` 6,960 = ` 840

Profit 840 2
\ Profit% = × 100 = ¥ 100 = 12.07% = 12 %
,
C.P. 6 960 29
Example 8: Sandeep bought a pen drive and sold it at a profit of 15%. If he had bought it at 25% less
and sold it for ` 20 more, he would have made a profit of 60%. Find the cost price of the pen
drive.
Solution: Let the C.P. of the pen drive be ` x.
15 3
Profit = 15% of x = ` x = ` x
100 20

173