SOLUTION: Johnny has some nickels and dimes in his pocket, and the change is worth $0.75. He has twice as many dimes as nickels. How many of each type of coin does Johnny have?

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Question 1199564: Johnny has some nickels and dimes in his pocket, and the change is worth $0.75. He has twice
as many dimes as nickels. How many of each type of coin does Johnny have?
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39623) About Me  (Show Source):
You can put this solution on YOUR website!
This is not the best way.... 
DIMES       NICKELS      for 75 CENT
  7           1
  6           3

Last combination is the one fitting description.


You want some algebra?
d and n
10d%2B5n=75andd%2Fn=2;
2d%2Bn=15
2%282n%29%2Bn=15
5n=15
n=3

Answer by ikleyn(52835) About Me  (Show Source):
You can put this solution on YOUR website!
.

According to the condition, it is possible to group coins in sets,  each containing  2  dimes and  1  nickel.

Each set is worth   2*10 + 5 = 25 cents.

So,  the number of such sets is  75/25 = 3,  giving  3  nickels and  6  dimes as the   ANSWER.

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Grouping is the method of solving such problems  MENTALLY,  without using equations.


To see many other similar solved problem by this method,  look into the lesson
    - Solving coin problems mentally by grouping without using equations
in this site.