Bunuel EducationAisle I notice that 9500 doesn't completely divide by 200, 300, and 350. So we know that there will be AT LEAST a combination of 2 or 3 of the above sq. feet. to cover the total area of 9500. But how can one come up with 2 - 3 instances (without spending too much time) to see that (1) is insuff.
What I thought was that 300 * 30 gives 9000. If I take one more 300 sq feet I'll get 9300. So 31(300 sq. feet) covers a total of 9300. We are left with 200 sq. feet. So 1(200 sq. feet) can be used to cover the remaining. Hence 1(200) + 31(300) = 9500. So here we have one instance.
Now if I look at 200 sq. feet. 4 * 2 = 8. So if I take 40 (200 sq. feet) I'll get 8000 sq. feet. The remaining 1500 sq. feet can be covered by 5 (300 sq. feet). So 40 (200 sq. feet) + 5 (300 sq. feet.) = 9500 sq. feet. Here we get another instance. Hence (1) is insuff.
BUT, this can take over 30-40 sec. Could you provide a more structured method of approaching this question. As you can see, I just took some random (smart) numbers and saw what is and isn't divisible by 9500.