El_Pollo
Solve using a system of equations:
There is a collection of nickels and dimes worth $3.30. There are 42 coins in all. How many are there of each kind?
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AriPotta
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5n + 10d = 330
n + d = 42
liza2
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n is the number of nickels and d is the number of dimes.
AriPotta
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so you gotta use the second equation to solve for d
AriPotta
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or n, but i would do d
AriPotta
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so what does d equal?
El_Pollo
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D=576
AriPotta
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no, what you gotta do it find out what d is compared to n.
so it's n + d = 42. what you do with that is subtract n from both sides to get d = 42 - n
AriPotta
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and then you can substitute 42 - n for d in the first equation
AriPotta
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so 5n + 10d = 330 would be 5n + 10(42 - n) = 330.
is this making sense?
El_Pollo
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Yes, but we have to have a system of equations
AriPotta
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the first thing i posted was our system of equations
AriPotta
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now we're solving it
El_Pollo
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Oh right sorry
AriPotta
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so do you know what to do from there? from 5n + 10(42 - n) = 330?
El_Pollo
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ok
El_Pollo
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so just distribute and then solve from there?
AriPotta
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yea, distribute the 10 into the parentheses and then solve for n and once you know how many nickels there are, just substitute that for n in the second equation and solve for d
El_Pollo
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i get a negative
AriPotta
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|dw:1349754629184:dw|
AriPotta
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does that make sense?
El_Pollo
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yes i see were i made my mistake i forgot the negative sign
AriPotta
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so now we know that 18 + d = 42 and we can solve for d
El_Pollo
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right plug in 18 in the n part
AriPotta
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yup, so how many dimes are there?
El_Pollo
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there's 24
AriPotta
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yep :) 24 dimes and 18 nickels