SOLUTION: The numerator of a fraction is seven more than twice the denominator. The value of the reciprocal of the fraction is 0.4. Find the original fraction. Could someone please help m

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Question 120847: The numerator of a fraction is seven more than twice the denominator. The value of the reciprocal of the fraction is 0.4. Find the original fraction.
Could someone please help me?

Found 3 solutions by checkley71, Earlsdon, solver91311:
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
(2x+7)/x=.4
2x+7=.4x
2x-.4x=-7
1.6x=-7
x=-7/1.6
x=-4.375 answer.
proof
(2*-4.375+7)/-4.375=.4
(-8.75+7)/-4.375=.4
-1.75/-4.375=.4
.4=.4

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Let N = the numerator and D = the denominator, so the fraction can be written as: N%2FD.
From the problem, you can write:
N+=+2D%2B7 so we'll substitute the N with 2D+7 to get:
%282D%2B7%29%2FD+ and the reciprocal of this is 0.4, so...
D%2F%282D%2B7%29+=+0.4 Replace the 0.4 with its fractional equvalent of 4%2F10
D%2F%282D%2B7%29+=+4%2F10 Now cross-multiply.
10D+=+4%282D%2B7%29 Simplify and solve for D.
10D+=+8D%2B28 Subtract 8D from both sides.
2D+=+28 Divide both sides by 2.
D+=+14 and...
N+=+2D%2B7
N+=+2%2814%29%2B7
N+=+35
The original fraction is:
N%2FD+=+35%2F14

Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!
Let x be the denominator. Twice the denominator is then 2x and seven more than that is 2x + 7, so our fraction is %282x%2B7%29%2Fx.

Since the value of the reciprocal of the fraction is 0.4, we can represent the reciprocal as 4%2F10. Therefore the value of the fraction itself must be 10%2F4.

Now we have enough information to create an equation:

%282x%2B7%29%2Fx=10%2F4

Multiply both sides by 4, and then multiply both sides by x:

4%282x%2B7%29=10x

Distribute:

8x%2B28=10x

Add -10x to both sides:

-10x%2B8x%2B28=10x-10x
-2x%2B28=0

Add -28 to both sides:

-2x=-28

Divide by -2:

x=14

Check the answer:

%282%2814%29%2B7%29%2F14=35%2F14=5%2F2

2%2F5=0.4, answer checks.