Here let take a=10 , c= 2 (for easy calculation we want to keep the value of b as integer and not fraction)

so b =\(\frac{(4 * 10)}{(2)}\)

or b= 20

Now a is halved = \(\frac{10}{2}\) = 5

and c is doubled = 2+2 = 4

Now b= \(\frac{(4 * 5)}{(4)}\) = 5

Therefore percentage decrease = \(\frac{(5-20)}{20}* 100\) = -75% i.e decrease
_________________

Thank you.

Explanation

Try plugging in values for a and c. Let a = 6 and c = 2.

Then b= =3. If a is halved, equal it will 3. If c is doubled, it will equal 4. So now, b= =3.

Because the question is looking for a percentage decrease, apply the percentage change formula:

\(\frac{12-3}{12}\times 100=\frac{9}{12}\times 100=75%\).
_________________

Hello from the GRE Prep Club BumpBot!

Thanks to another GRE Prep Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.