Data Sufficiency

A jar contains 30 marbles, of which 20 are red and 10 are blue. If 9 of the marbles are removed, how many of the marbles left in the jar are red?
(1) Of the marbles removed, the ratio of the number of red ones to the number of blue ones is 2 : 1.
(2) Of the first 6 marbles removed, 4 are red.

A

So, 30 marbles, which 20 red and 10 blue. Take 9 marbles, how mane red left in the jar?

(1) Says that the ratio of red to blue is 2:1 among the 9 taken.

Basically, you took 6 red and 3 blue out of the jar (only possible ratio 2:1 in 9 marbles). Which let´s you calculate the remaining red ones (20-6). SUFF

(2) Of the first 6 marbles removed, 4 are red
Doesn´t gives data about the other 3 taken ones, so now chance of giving an accurate answer on how many red ones remain in the jar. INSUFF

Answer is A

IMO A


Total 9 marbles removed..

Ratio 1:2 so

we can find the no. of red removed.....

Suff


2. next 3 can be anynumber for Red

Insuff