by Cece
(Bakersfield California)
A stationery store sells a dozen ballpoints pens for $3.84, which represents a 20% discount from the price charged when a dozen pens are bought individually. How much does it cost to buy three pens?
Solution
Let x be the price of a dozen ballpoints pens without the 20% discount.
x - 20%x = 3.84
x - 0.20x = 3.84
0.80x = 3.84
x = 3.84/0.80
x = 4.8
4.8 is the price for 12 ballpoints pen with no 20% discount.
The price of 1 ballpoints pen is 4.8 / 12 = 0.4
The price of 3 pens is 3 × 0.4 = 1.2
Oct 15, 18 11:05 AM
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Oct 15, 18 11:05 AM
why the rule of 72 works- math explanation of where the 72 came from.
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