Question

Lisa's piggy bank contained 21 dimes, nickels, and pennies. The total in the piggy bank was $1.21. Lisa removed all the dimes from the piggy bank. This left only 41 cents in the bank. How many pennies were in the bank?

Answer 1

x = number of dimes
y = number of nickels
z = number of pennies

x + y + z = 21
(.1)*x + (.05)*y + (.01)*z = 1.21
(.05)*y + (.01)*z = .41

Take equation 3 and solve for y:

(.05)*y = .41 - (.01)*z

y = 8.2 - (.2)*z

Plug this value for y into equation 1 and solve for x:

x + (8.2 - (.2)*z) + z = 21

x + z - (.2)*z = 21 - 8.2

x + (.8)*z = 12.8

x = 12.8 - (.8)*z

Now, plug your values for x and y into equation 2 and solve for z:

(.1)*(12.8 - (.8)*z) + (.05)*(8.2 - (.2)*z) + (.01)*z = 1.21

1.28 - (.08)*z + .41 - (.01)*z + (.01)*z = 1.21

1.69 - (.08)*z = 1.21

(.08)*z = .48

z = 6

Now, plug your value for z back into the simplified equation for y:

y = 8.2 - (.2)*(6)

y = 7

So, Lisa had 7 nickels and 6 pennies in the bank.

Answer 2

That is a lot of work!..

Answer 3

im really bored lol

Answer 4

Oh.