Question

Justin is exchanging dollars for rolls of quarters and rolls of dimes at a bank. Each roll of quarters has a value of $10 and each roll of dimes has a value of $5. He exchanges $90 and receives 11 rolls of coins. How many of each type of roll of coins did he receive?

Answer 1

Well, it really depends but it could be 9 rolls of quarters, 5 rolls of quarters and 8 rolls of dimes, 4 rolls of quarters and 10 rolls of dimes, 3 rolls of quarters and 12 rolls of dimes, etc.

Answer 2

Justin got 7 rolls of quarters and 4 rolls of dimes.

Explanation:

Let the roll of quarters be x

Let the rolls of dimes be y

As total money received is $90, the equation becomes;

`10x+5y=90` .....(1)

And he got 11 roll of coins, so equation becomes;

`x+y=11` or
`x=11-y` .... (2)

Substituting the value of x from (2) in (1)

`10(11-y)+5y=90`

`=> 110-10y+5y=90`

`=> -5y=-110+90`

`=> -5y=-20`

So, y = 4

As
`x=11-y`

So,
`x=11-4`

x = 7

Hence, Justin got 7 rolls of quarters and 4 rolls of dimes.