SOLUTION: Phil has 50 nickels and dimes worth $4.15. How many dimes does he have?

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Question 542374: Phil has 50 nickels and dimes worth $4.15. How many dimes does he have?
Found 2 solutions by neatmath, josmiceli:
Answer by neatmath(302) About Me  (Show Source):
You can put this solution on YOUR website!

Our two variables are:

n number of nickels

d number of dimes

Our two equations are now:

n%2Bd=50

.05%2An%2B.10%2Ad=4.15

We can then solve this system of two equations by elimination or substitution.

I will try substitution. I will solve for n in the first equation:

n=50-d

Then I will multiply the second equation by 100 to make it easier to deal with:

5n%2B10d=415

Then I will substitute 50-d in for n in our new equation:

5%2A%2850-d%29%2B10d=415

250-5d%2B10d=415

250%2B5d=415

5d=165

d=33

Thus we now know that we have 33 dimes! (which is the answer)

And of course, we also know that we have 17 nickels.

You can easily double check this by using our original second equation.

I hope this helps!

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let n = number of nickels
Let d = number of dimes
given:
(1) +n+%2B+d+=+50+
(2) +5n+%2B+10d+=+415+ ( in cents )
------------------
Multiply both sides of (1) by 5 and
subtract (1) from (2)
(2) +5n+%2B+10d+=+415+
(1) +-5n+-+5d+=+-250+
+5d+=+165+
+d+=+33+
and, since
(1) +n+%2B+d+=+50+
(1) +n+%2B+33+=+50+
(1) +n+=+17+
He has 33 dimes
check answer:
(2) +5n+%2B+10d+=+415+
(2) +5%2A17+%2B+10%2A33+=+415+
(2) +85+%2B+330+=+415+
(2) +415+=+415+
OK