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PLEASE HELP ME ANSWER THESE QUESTIONS will give BRAINLIEST

1. The numerator of a certain fraction is 3 more than the denominator. If 3/2 is added to the fraction, the result is 4. Find the fraction.

2. If 3/8 is added to five times the reciprocal of a number, the result is 1. Find the number.

3. One car travels 390 miles in the same amount of time it takes a second car traveling 3 miles per hour slower than the first to go 372 miles. What are the speeds of the cars?

Respuesta :

sqdancefan

9514 1404 393

Answer:

  1. 5/2
  2. 8
  3. 65 mph, 62 mph

Step-by-step explanation:

The first two problems can be solved in your head by working backward from the end result.

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1. After 3/2 is added, the result is 4. Then we must be adding 3/2 to 4 -3/2 = 5/2. We notice that 5/2 already has the numerator 3 more than the denominator, so the fraction of interest is 5/2.

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2. If 3/8 is added to a number giving a result of 1, the number must be 1 -3/8 = 5/8. That is 5 times 1/8. The number of interest is the reciprocal of 1/8, so is 8.

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3. Let x represent the speed of the faster car. Then x-3 is the speed of the slower car, and the two times are ...

  time = distance/speed

  390/x = 372/(x-3)

  390(x -3) = 372x . . . cross multiply

  18x = 1170 . . . . . . . add 1170-372x

  x =  65 . . . . . . . . . . divide by 18

The speeds of the cars are 65 mph and 62 mph.

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