jayycruz59
06.10.2019 •
Mathematics
Arestaurant bill comes to $2.85 was paid using quarters and dimes only. if twice the number of quarters is 6 less than 4 times the number of dimes, how many quarters were used?
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Ответ:
Read the rest of the question. There are TWO sentences. That is TWO equations. That means TWO variables. What else is involved? WRITE: Let Y = the number of .
Rewrite each sentence as an equation (something EQUALS something) with "X" and "Y".
Remember that "less than" is a BACKWARDS subtraction: 2 less than 5 is "5-2".
For the first sentence, remember that quarters are worth $0.25, so the worth of a number of quarters is 0.25 TIMES the number of quarters. Dimes are worth $0.10, so the worth of a number of dimes is 0.10 TIMES the number of dimes. Remember that the TOTAL worth is a SUM (add to equal the total bill).
Solve one equation (either one) for Y and substitute that formula into the other equation. Solve for X. Done.
2x=4y-6 -> y=(2x+6)/4
285 = 25x+10y = 25x + 5(x+3) = 30x + 15 -> 270 = 30 x -> x=9 (y=24/4=6)
Alternate solution - no algebra. Trial and Error:
Pick a number of quarters: Maybe 10. That makes $2.50, which leaves $0.35. That means 3.5 dimes. But twice 10 quarters is 20 and 6 less than 4 times 3.5 dimes is 8. But 20 is not equal 8, it is 12 too big.
Try a different number. Maybe 11. That makes $2.75, which leaves $0.10. That means 1 dime. But twice 11 quarters is 22 and 6 less than 4 times 1 dime is -2. But 22 is not equal -2. It is 24 too big. Worse than before!
Try again. That last guess was worse, so go in the other direction. Keep trying until you find the answer.
Ответ:
3x - 8 = -2
3x -8+8 = -2 +8
3x = 6
3x/3 = 6/3
x = 2
s
x - 6
( 2-6)
= -4
that is the value of x -6
= -4