Question

Charlie put postage worth $1.29 on a package he sent to his sister. He used only 16-cent stamps and 7-cent stamps. How many each of type of stamp did he use?
Show work and explain it.

Answer 1

Any help?

Answer 2

Make 2 equations.

Answer 3

Wait! Are you sure the question's complete?

Answer 4

What do you mean?

Answer 5

And I think yes the question is complete that is what is on my paper.

Answer 6

@dumbcow @Zarkon

Answer 7

Suppose number of 16 cents stamps as "x"
Suppose number of 7 cents stamps as "y"

16x + 7y = 129 - 1

I can't make up the second question.

Answer 8

@lgbasallote

Answer 9

Why did you subtract 1 ?

Answer 10

No, that's sign for equation 1.

Answer 11

I still think that the question is incomplete.. They should've given you the total number of stamps.

Answer 12

You are probably right; but do you know what is the exact answer?

Answer 13

Yes. You can solve it using a shortcut.

Answer 14

How?

Answer 15

As now you have the equation,
16x + 7y = 129

Insert a particular value of x and y and make the answer equal to 129,

Answer 16

Take x = 5, y = 7

Answer 17

this question isn't complete...

Answer 18

it should state how many stamps there are overall

Answer 19

I know but that Is what my teacher gave me.

Answer 20

The stamps are: 5+7 = 12

Answer 21

But you can see figure it out because at least the gave you the cents for each stamp and the total stamps.

Answer 22

So there is 12 stamps in total?

Answer 23

Yes, i solved it mentally.

Yes 12 stamps.

Answer 24

Thank you. :) for your help.

Answer 25

you could also just graph the equation as a line...there are infinite solutions, however you need an integer solution

\[y = \frac{129-16x}{7}\]

Answer 26

there are infinite possibilities then

Answer 27

haha well mathematically yes, but practically there are finite number of positive integer solutions

Answer 28

I agree. This question was abit confusing for me though.