Question

A takes $5$ days less than $B$ to complete the work. Both complete the work in $6$ days. In how many days $A$ complete the work?

• A. $10$
• B. $15$
• C. $20$
• D. $30$

Answer 1

The correct option is A $10$

From given, we have,

$\frac{1}{x}+\frac{1}{x+5}=\frac{1}{6}$

$6(x+5)+6x=x(x+5)$

$x^2+5x-30=12x+30-30$

$x^2-7x-30=0$

$(x-10)(x+3)=0$

$\therefore x=-3,10$

Days can't be negative.

Therefore, the number of days A uses to complete the work is $10$ days.