The numerator of a fraction is 4 less than the denominator. If the numerator is decreased by 2 and denominator is increased by 1, then the denominator is eight times the numerator. Find the fraction.
Solution
Let the numerator and denominator of the fraction be x and y respectively. Then the fraction is `x/y`
The numerator of the fraction is 4 less the denominator. Thus, we have
`x = y -4`
` ⇒ x -y =-4`
If the numerator is decreased by 2 and denominator is increased by 1, then the denominator is 8 times the numerator. Thus, we have
` y + 1 = 8(x-2)`
`⇒ y + 1= 8x -16`
` ⇒ 8x -y = 1+16`
`⇒ 8x - y =17`
So, we have two equations
` x - y = -4`
` 8x -y =17`
Here x and y are unknowns. We have to solve the above equations for x and y.
Subtracting the second equation from the first equation, we get
`( x -y)-(8x -y)=-4-17`
`⇒ x - y -8x +y =-21`
` ⇒ -7 x =-21`
` ⇒ 7 x =21 `
` ⇒ x =21/7`
` ⇒ x = 3`
Substituting the value of x in the first equation, we have
` 3- y =-4`
`⇒ y = 3+4 `
` ⇒ y = 7`
Hence, the fraction is `3/7`