Hi Shubhi09,

The prompt gives us an equation for the number of gallons of gas used per mile at a particular speed:

(1/12) + (K)(V^2) gallons of gas are used per mile when the truck travels at a speed "V" (in miles per hour). We're also told that K is a constant - meaning that it is NOT a variable that changes (it's a value, but we don't know exactly what the value is yet). We are asked how fast the truck must travel to us 5/12 of a gallon of gas per mile.

Fact 1 gives us the additional information that K = 1/10800. Plugging in this value into the given equation, we have....

(1/12) + (1/10800)(V^2) = 5/12

(1/10800)(V^2) = 4/12

(V^2) = (4/12)(10800)

In the situation described, since "V" refers to speed, then it must be a POSITIVE number. Thus, the above equation would have just ONE solution. If you really wanted to do the math, then you could find that solution, but that work is ultimately unnecessary. With the information in Fact 1, there will be just one answer, so Fact 1 is SUFFICIENT.

GMAT assassins aren't born, they're made,
Rich
_________________