What number, when added to the numerator and to the denominator of 5/8, results in a fraction whose value is 0.4?

1 Answer
Apr 28, 2018

n=-3

Explanation:

let n be that number

(5+n)/(8+n)=0.4

Many ways to solve, I prefer turning it into a fraction:

(5+n)/(8+n)=2/5

2(8+n)=5(5+n)

16+2n= 25+5n

-9=3n

n=-3

Another way:
(5+n)/(8+n)=0.4

5+n=0.4(8+n)

5+n= 3.2+0.4n

1.8= -0.6n

n=-3