Jacy has a collection of 140 coins worth $19.00. She has only nickels, dimes, and quarters. The difference in the number of dimes and the number of quarters is 10. Using matrices, how many nickels are in Jacy's collection? 38 50 95 130

She has 38 nickels

Step-by-step explanation:

Let's define:

N as the number of nickels, D as the number of dimes, and Q as the number of quarters.

She has 140 coins in total, so we can writen:

N + D + Q  = 140.

And the total value is $19.00

Then we have:

N*0.05 + D*0.10 + Q*0.25 = 19

And "The difference in the number of dimes and the number of quarters is 10."

D - Q = 10.

So we have a system of 3 equations and 3 variables:

N + D + Q  = 140.

N*0.05 + D*0.10 + Q*0.25 = 19

D - Q = 10.

First, let's isolate one of the variables in the third equation, i will isolate D.

D = 10 + Q.

Now we can replace this in the other two equations:

N + (10 + Q) + Q = 140

N*0.05 + (10 + Q)*0.10 + Q*0.25 = 19.

Now we can isolate Q in the first equation:

N + 10 + 2*Q = 140

2*Q = 140 - 10 - N

Q = 130/2 - N/2. = 65 - N/2

Now we can replace this in the other equation:

N*0.05 + 10*0.10 + Q*(0.10 + 0.25) = 19

N*0.05 + 10*0.10 + (65 - N/2)*( 0.35) = 19

Now we can find the number of nickels.

N*0.05 + 1 + 22.75 - N*0.175 = 19

23.75 - N*(0.175 - 0.05)  = 19

23.75 - 19 = N*0.125

4.75/0.125 = N

38 = N

She has 38 nickels

the answer is 489

step-by-step explanation: