1) A man sells his scooter for $18000 making a profit of 20%. How much did the scooter cost him?

Let c.p = $100

As there is profit % as 20 so s.p = 100 + 20 = $120

Let the c.p of the scooter be $x

Now make proportions as

100/x = 120/18000

Cross multiply

120x = 100 . 18000

120x = 1,800,000

So, x = 1,800,000/120

x = $15000

Hence the cost price of the scooter is $15000.

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2) By selling an AC for $ 20,000, I lose 20%. What did I pay for it?

We have S.P. = $ 20,000 and loss = 20%.

Let c.p = $100

As there is loss % as 20 so s.p = 100 - 20 = $80

Let the c.p of the scooter be $x

Now make proportions as

100/x = 80/20,000

Cross multiply

80x = 100 . 20,000

80x = 2,000,000

So, x = 2,000,000/80

x = $ 25000

Hence the cost price of the AC is $25,000.

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3) SP = $450 and profit % = 50, find CP.

Let c.p = $100

As there is profit % as 50 so s.p = 100 + 50 = $150

Let the c.p of the scooter be $x

Now make proportions as

100/x = 150/450

Cross multiply

150x = 100 . 450

150x = 45,000

So, x = 45,000/150

x = $300

Hence, CP = $300

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4) A shopkeeper sells one transistor for $ 840 at a gain of 20% and another for $ 960 at a loss of 4%. His total gain or loss percent is:

1st Transistor Let c.p = $100 As there is profit % as 20 so s.p = 100 + 20 = $120 Let the c.p of the scooter be $x Now make proportions as 100/x = 120/840 Cross multiply 120x = 100 . 840 120x = 84,000 So, x = 84,000/120 x = $700 Hence, CP = $700 |
2nd Transistor Let c.p = $100 As there is loss % as 4 so s.p = 100 - 4 = $96 Let the c.p of the scooter be $x Now make proportions as 100/x = 96/960 Cross multiply 96x = 100 . 960 96x = 96,000 So, x = 96,000/96 x = $1000 Hence, CP = $1000 |

∴ Total CP = 700 + 1000 =$1700

Total SP = 840 + 960 = $1800

Profit = SP - CP

Profit = 1800 -1700 = $100

Profit % = (Profit/CP )x100

Profit % = (100/1700)x100

Profit % = 5.88%

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