Question

PLEASE HELP: I have 38 coins. They consist of dimes and quarters. How many dimes do I have? I have $6.95

Answer 1

how many dimes and quarters do you have?

Answer 2

38 Total

Answer 3

d + q = 38

each d is worth .10 each q is worth .25 sooo

.10 d + .25 q = 6.95

you understand this?

Answer 4

Yes, But it has to equal 38 coils. I got that far haha

Answer 5

by substitution, let d = 19+n, and q=19-n

does 19+n + 19-n = 38?

Answer 6

Yes..

Answer 7

then lets solve for n

.10(19+n) + .25(19-n) = 6.95

when we know n we can know d and q

Answer 8

95..?

Answer 9

Wait.. I messed up somewhere

Answer 10

we could have just as well defined it:

d = 38-n, q=n

.10(38-n) + .25n = 6.95 is another way to approach it ....

Answer 11

21

Answer 12

the idea is to set up some convenient one variable setup that defines d + q for all n

the second setup, n=21 yes :)

Answer 13

d = 38 - 21, q = 21

Answer 14

in the first setup, n=-2

d = 19 +-2, q = 19 - -2

we get the same results

Answer 15

17 dimes?

Answer 16

yep

Answer 17

:DDD

Answer 18

I tried the same method but I can't get it right

Answer 19

IT WORKED !

Answer 20

:) it better worked lol

Answer 21

this type of substitution is very ancient, the greeks way back when used to use it.