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10D + 25Q = 170 and D = Q + 3Substitute: 10(Q + 3) + 25Q = 170ie 10Q + 30 + 25Q = 170ie 35Q = 140so Q = 4, making D = 7
Let the number of nickels, dimes and quarters be n, d, q respectively. Then n +d + q = 30 5n + 10d + 25q = 550 But d = 2n, so: n + 2n + q = 30 => 3n + q = 30 5n + 10(2n) + 25q = 550 => 25n + 25q = 550 => n + q = 22 Which gives two simultaneous equations to solve, resulting in: n = 4, q = 18 So there are 18 quarters (plus 4 nickels and 8 dimes).
5n + 25q = 490; n = 2q so: 10q + 25q = 490 ie 35q = 490 so q = 14 and n must be 28. 14 x 25c = $3.50, 28 x 5c = $1.40, total $4.90. ...and there you have it!
This is a system of equations. Let d= number of dimes. q= number of quarters. d+q=1000 -> 10d + 10q = 10000 .10d+.25q=199.90-> -10d+(-25q)=-19990 Multiply each equation to get one of the variables to drop out. Add the equations. (-15q)=(-9990) q=666 1000-666=334 There are 666 quarters and 334 dimes.
Given: 10d + 25q = 895 cents d + q = 52 coins Multiply everything in the second equasion by 10 (to get rid of the dimes). 10d + 10q = 520 Subtract this 3rd equation from the 1st equation: 10d + 25q = 895 10d + 10d = 520 Giving you: 15q = 375 Divide both sides by 15 and you get q = 25 This means you have 25 quarters ($6.25) and 27 dimes ($2.70) CHECK: 25 quarters + 27 dimes = 52 coins (CORRECT) $6.25 + $2.70 = $8.95 (CORRECT)