SOLUTION: I need help. You have a pile of quarters and a pile of dimes. between the two piles, there are a total of 20 coins with a value of $3.80. how many of the coins are quarters? How ma

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Question 1124559: I need help. You have a pile of quarters and a pile of dimes. between the two piles, there are a total of 20 coins with a value of $3.80. how many of the coins are quarters? How many are dimes? Thank you
Answer by math_helper(2461) About Me  (Show Source):
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Let d = number of dimes, q = number of quarters

(1) d+q = 20 (from the given quantity of coins)
(2) 10d + 25q = 380 (equation derived from description of value of coins, expressed in cents)
10*(1) ==> 10d+10q = 200
subtract (2) -10d - 25q = -380
-15q = -180

q = 180/15 = 12 —(from (1))—> d = 8
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Ans: There are 12 quarters and 8 dimes.
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Check: 25(12) + 10(8) = 300 + 80 = 380 cents = $3.80 (ok)