Question

John is $1$ year younger than his brother David. If the product of their ages is $56$. Find the age of David.

• A. $5$
• B. $6$
• C. $7$
• D. $8$

Answer 1

The correct option is D $8$

Let $x=$ age of brother David
Then, $x-1=$ age of John---(1)
So, product of their age $=x(x-1)=56$
$x^2-x-56=0$
On factoring, we get,
$(x-8)(x+7)=0$
$x-8=0,x+7=0$
$x=8$ or $x=-7$
So, the age difference is $8$ years.