The numerator of a certain fraction is 5 less than the denom

[degreeplus]

I need help solving a question.
question:

The numerator of a certain fraction is 5 less than the denominator. If the fraction is equal to (3/4), what is the denominator of this fraction?
(a) 8
(b)12
(c)16
(d)20
(e)24

My book says the answer is (d), but I have no clue on how they arrived to that answer. The wording of this problem confuses me

This is how I see it:

"the numerator of a certain fraction is 5 less than the denominator"
*n= numerator
*d= denominator
[n(3/4)]-5=d
or n(3/4)=d+5

see Im unsure of what they mean by "of a certain fraction." Is that the fraction they give you-(3/4)- or is it some unknown fraction?

 

[stapel]

A "certain fraction" just means "we're not telling you which one"; you have to figure it out.

Pick a variable for the value of the denominator. Write an expression, in terms of this variable, for the numerator. Form the fraction. Set it equal to the given equal value. Solve the resulting equation for the value of the variable. Back-solve for the value of the fraction.

If you get stuck, please reply showing how far you have gotten in working through these steps. Thank you.

Eliz.

 

[arthur ohlsten]

let n be the numerator and d the denominator
but n=d-5
number =[d-5]/5
3/4= [d-5]/d multiply both sides of the equal sign by d
3d/4 =d-5 multiply both sides by 4
3d=4d-20 subtract 3d from each side
0=d-20 add 20 to each side
20=d answer

Arthur

 

[degreeplus]

Thanks for the replies. Man I just hate it when I overcomplicate things. I had soemthing close to n=d-5 but I misinterpreted and put n=d+5 so then I tried looking at it differently with n of a certain fraction = d+5 which has 2 flaws. Well thanks again for the help, really appreciate it