Question

a collection of dimes an nickels is worth $3.30. if there are 42 coins in all, how many of each kind of coin is there ?

Answer 1

Answers:

24 dimes

18 nickels

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Work Shown:

d = number of dimes

n = number of nickels

10d = value of all the dimes in cents

5n = value of all the nickels in cents

10d+5n = total value of all the coins in cents

$3.30 = 3.30*100 = 330 cents

so one equation is 10d+5n = 330

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Let's set up the second equation

we have 42 coins, so n+d = 42

subtract d from both sides to get n = 42-d

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Go back to the first equation and apply substitution to solve for d.

10d+5n = 330

10d+5(42-d) = 330 ... plug in n = 42-d

10d+5(42)+5(-d) = 330 ... distribute

10d+210-5d = 330

5d+210 = 330

5d = 330-210 ... subtract 210 from both sides

5d = 120

d = 120/5 ... divide both sides by 5

d = 24

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Now we can use that to find n.

n = 42-d

n = 42-24 ... plug in d = 24

n = 18

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Check:

n = 18 nickels

5*n = 5*18 = 90 cents from just the nickels

d = 24 dimes

10*d = 10*24 = 240 cents from just the dimes

5n+10d = 90+240 = 330 cents = $3.30 total from all the coins

n+d = 18+24 = 42 coins total

Answers are confirmed