An algebra problem by Victor Paes Plinio

Algebra Level 2

Stamp riddle

Jane want to clear you garage and search for old things. She find an part of the old stamp collection from his grampa. In the first part of the book have the 50 cents and 1dollar stamps. In the front of the book have this riddle:

"In here only have 50 cents and 1 dollar stamps. For make this part of my collection, I spent 100 dollars with 160 stamps. What is the number of 1 dollar stamps?"

sorry, I forget to put a title.

The answer is 40.

3 solutions

Mohd Naim Mohd Amin
Mar 26, 2014

Hello,peace be upon you,

Let x = $0.50 , y =$1, given that total stamps= 160, total money spent = $100,

x + y = 160, x = 160 - y -------------> substitute this into the 2nd equation,

0.5x + y = 100(2nd equation),

0.5(160-y) + y = 100,

80 - 0.5y + y =100,

0.5 y = 100-80

y = 20 / 0.5 = 40

x = 160 - 40 =120

therefore,there 120 stamps for $0.50 stamp, and 40 stamps for $1....there the answer is 40...

thanks...

Thank you, Mohd Naim Mohd Amin. I was able to follow the logic very well. Peace be upon you, as well.

John Roldan - 7 years, 2 months ago

you're welcome bro...

MOHD NAIM MOHD AMIN - 7 years ago

V Vishnu Prasad
Mar 26, 2014

If you are good in mind calculation,could solve it more easily.Total number of stamps is 160 and total cost is $100.It consist of 50 cents & $1 stamps. Definitely no: of $1 stamp should be less than 100(coz total cost is only $100).$1 stamp should be less than 50.Now,i think, one can easily assume 40 out of 160 stamps is of $1 and rest 120 are of 50 cents. (40 * $1) + (120 * 50 cents) == $100, which is the total cost of 160 stamps No: of $1 stamps == 40

Blesson Roy
Mar 31, 2014

Let number of 1 dollar stamps be : X therefore number of 50 Cents stamps are : 160-X Therefore, X+((160-X)/2) = 100. Hence X = 40

An algebra problem by Victor Paes Plinio

The answer is 40.

3 solutions

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