Help with a Word problem

Question

Imagine a new pasture with grass growing on it. Every day after the seeds have germinated, the number of blades of grass in the pasture triples. After 18 days, the entire pasture is completely covered in grass. How many days did it take for the pasture to be one-third covered in grass? 

Answer 1

For Elementary Math, this is simply a "think about it" problem, not one that uses exponents.

If "Every day . . . the number of blades of grass in the pasture triples" and "After 18 days, the entire pasture is completely covered in grass," then the 'complete covering' is triple the amount covered at 17 days (one day before).

At 17 days, 1/3 (that is 33 1/3%) of the pasture was covered, then in 1 day the amount tripled (that is, 3*(1/3), then the amount covered after 18 days is 1 (or one whole, or 100%).

One of the very important things to learn with MATH is that it can be very useful when you have to work backward from the current situation. For example: If it is now 3:00 PM, what time was it 17 minutes and 30 seconds ago?

Answer 2

It took 17 days to hit 33%.

3^18=3874204890

/3=1291401630

=3^17