Question

The shopkeeper brought a box containing x files for $20. he could have brought 5 more files if each file cost 20 cents less.(a) Form an equation in x and show that it reduces to x^2 + 5x - 500 = 0

Answer 1

1$=100 cents

$\implies$ 20 cents = 0.2 $

$\implies(\frac{20}{x}-0.2)(x+5)=20$

$(20-0.2x)(x+5)=20x$

$20x+100-0.2x^2-x=20x$

$0.2x^2+x-100=0$

$x^2+5x-500=0$