math
posted by Cheril on .
Select the equation that solves this problem:
Eight coins (dimes and nickels) are worth 60 cents. How many dimes are
there?
a. 10d + 25(11  d) = 170
b. 10d + 25(8  d) = 170
c. 10d + 5(8  d) = 60
d. 10d + 5(11  d) = 60

C.
d = the number of dimes, while 8d equals the numbers of nickels, if you multiply the number of each coins by their value ( 10 cents or 5 cents ) and add them, you should get 60 
A nickel is worth 5 cents and a dime is worth 10 cents.
n = numbers of a nickels
d = numbers of a dimes
n + d = 8
n = 8  d
Value of money :
10 ¢ * d + 5 ¢ * n = 60 ¢
10 d + 5 n = 60
10 d + 5 ( 8  d ) = 60
Equation c.
10 d + 5 ( 8  d ) = 60
10 d + 5 * 8 + 5 * (  d ) = 60
10 d + 40  5 d = 60
5 d + 40 = 60
5 d = 60  40
5 d = 20 Divide both sides by 5
d = 20 / 5
d = 4
n = 8  d = 8  4 = 4
4 dimes and 4 nickels
4 * 10 ¢ + 4 * 5 ¢ =
40 ¢ + 20 ¢ = 60 ¢