sandy wrote:
Maria removed \(\frac{5}{6}\) of the cookies from a jar, and then Andrea removed \(\frac{3}{5}\) of the remaining cookies from the same jar. Which of the following could NOT be the number of cookies originally in the jar?
Indicate all possible values.
A. 6
B. 15
C. 30
D. 60
E. 200
F. 210
G. 340
Let x = original # of cookies
So, AFTER (5/6)x cookies are removed, there are
x/6 cookies REMAINING.
This tells us that
x must be divisible by 6.
Andrea removed 3/5 of the REMAINING cookies.
So, she removed 3/5 of the x/6 remaining cookies.
(3/5)(x/6) =
x/10So,
x must be divisible by 10So,
x must be divisible by 6 AND by 10Examine the answer choices:
A. 6 NOT divisible by 10.
KEEPB. 15 NOT divisible by 10.
KEEPC. 30 is divisible by 6 AND 10. ELIMINATE
D. 60 is divisible by 6 AND 10. ELIMINATE
E. 200 NOT divisible by 6.
KEEPF. 210 is divisible by 6 AND 10. ELIMINATE
G. 340 NOT divisible by 6.
KEEPAnswer: A, B, E, G
Cheers,
Brent