GMAT prep - Rate of chemical

[auntsom]

A rate of a certain chemical reaction is directly proportional to the square of tge concentration of chemical A present and inversely proportional to a concentration of chemical B present. If the concentration of chemical B is increased by 100%, which of the following is clost to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

1. 100% decrease
2. 50% decrease
3. 40% decrease
4. 40% increase
5. 50% increase

I have no idea what it is about. Thanks for explanation.

[auntsom]

I'm so sorry, I should have posted it in problem solving section.

Sorry for my mistake.

[cubicle_bound_misfit]

Option D.

sqauare root of 2 (approx)= 1.4

Regards,

[Vinni]

Lets say rate = K * (a^2 / b) - Eq1
Now b is increased by 100%

therefore new
rate = K * (a1^2/2b) - Eq2
where new a is = a1

Eq1 = Eq2
(a^2 / b) = (a1^2/2b)

a1 = Sqrt(2) * a = 1.414a

Clearly a is approx 40% increased!
D is the answer!

OA please?

[auntsom]

You're right, answer is D.

Thanks guys for explanation.