Grade Penny
5 stars to the person who can answer this grade 9 algebra question?
“Devin has pennies, dimes and quarters. He has a total of $8.70. There are two times as many pennies as quarters. There are six times as many dimes as quarters. How many of each coin does he have?”
I need you to write the equation, and give the value for the variable. My teacher is giving chocolate to whoever can do it!!! Thanks so much 
Pennies ($0.01) = x , Dimes ($0.10)= y , Quarters ($0.25) = z
There are two times as many pennies as quarters:
x = 2z
There are six times as many dimes as quarters;
y = 6z
Equation:
($0.01)x + ($0.10)y + ($0.25)z = $8.70
Substitute x and y:
($0.01)2z + ($0.10)6z + ($0.25)z = $8.70
Solve for z:
$0.87z = $8.70
z = $8.70/$0.87
z=10
Pennies:
x = 2z
x = 2(10)
x = 20
Dimes:
y = 6z
y = 6(10)
y = 60
Quarters
z=10
Plug back into equations to check:
($0.01)x + ($0.10)y + ($0.25)z = $8.70
($0.01)20 + ($0.10)60 + ($0.25)10 = $8.70
$0.20 + $6.00 + $2.50 = $8.70
$8.70 = $8.70
Enjoy your chocolate!
John Thompson’s Modern Piano Course Grade 1 No.7 A Song of Penny Candy 一分糖的歌