Ease Into Prep with a GMAT^® Question of the Day

Don't bother with complicated equations—just logic this one out. Maisie has 6 rabbits today and they double every 8 months. Calculate what happens every 8 months for the next 4 years, also known as 48 months:

Today: 6 rabbits
8 months: 12 rabbits
16 months: 24 rabbits
24 months: 48 rabbits
32 months: 96 rabbits
40 months: 192 rabbits
48 months: 384 rabbits

The calculations get a little annoying for the last two time periods. If you need a precise answer, use nearby easier numbers and then correct for your estimation. For example, 96 × 2 is really close to 100 × 2 = 200, but subtract 4 × 2 for the overcount: 200 – 8 = 192.

But before you bother to calculate precise numbers, glance at the answers! In this case, they're pretty far apart, so you can go for pure estimation:
40 months: A little less than 100 × 2 = a little less than 200
48 months: A little less than 200 × 2 = a little less than 400
Only answer (E) is close.

The correct answer is (E).