Question

A machine takes $2$ litres of petrol to start and then $3$ litres per hour while running. What is the total amount of petrol used if machine run for $3$ hours?

• A. $8$
• B. $9$
• C. $10$
• D. $11$

Answer 1

Answer: (D)

$11$

Amount of petrol used $=y$
No. of hours for which machine will work $=x$
$\therefore y=3x+2$
$\Rightarrow y-3x-2=0$
$\Rightarrow -3x+y-2=0$
$a=-3,b=1,c=-2$
$a+b+c=-3+1+(-2)=-4$
If machine runs for $3$ hours, $x=3$

$\Rightarrow y=3\times 3+2=11$