Critical Reasoning

paddle_sweep wrote:What's wrong with 'C'?

Testluv wrote:

paddle_sweep wrote:What's wrong with 'C'?

There can be other ways that the economy will collapse.

We know that:

IF Russia avoids economic collapse, THEN 40% is possible.

We can't just switch these two around. That is, "IF A, THEN B", does not imply "IF B, THEN A".

If you are in Pune then you are in India; but that does not mean that if you are in India that you are in Pune.

You need gas to drive a car. So, if the car is running, we know there is gas in it. But if there is gas in the tank, we don't know for sure that the car is running (because there are other things you need to run the car--transmission, steering wheel, etc).

IF A then B does imply that "if No B, then No A" (this is called the contrapositive). If you are not in India, then you are definitely not in Pune. Likewise, if there is NO gas in the tank, then we definitely can't run the car.

In other words, choice C confuses suff/nec.

tpr-becky wrote:I disagree becuase answer choice D includes "and a 60 percent increase is probable" no where in the sentence does it talk about a 60%

the right asnwer is B because if russia doesn't reach 20% it WILL collapse and if it reaches 20% then 40% is possible. therefore if 40% is impossible then they must not have reached the 20% which means the economy will collapse.

Testluv wrote:

deepesh.gupta wrote:If Russia avoids economic collapse, then it increases GNP by 20%.
(avoid ec. coll.----> increase GNP 20%)

The second sentence yields:

if it increases GNP by 20%, then 40% is possibe.
(increase GNP 20%----> 40% possible)

Note that the right hand side of the first conditional statement is also the left-hand side of the second. Thus:

if Russia avoids economic collapse, then 40% is possible,

whose contrapositive is:

if 40% is NOT possible (ie, IS impossible), then Russia will NOT avoid economic collapse (ie, WILL collapse).

sir,
so you mean A-->B, B-->C then A-->C this part I do understand
but how can NOT C-->NOT A???
that is like saying, if floor is weet then it rained, if not rained then floor is not weet.

sir,
so you mean A-->B, B-->C then A-->C this part I do understand
but how can NOT C-->NOT A???
that is like saying, if floor is weet then it rained, if not rained then floor is not weet.

Testluv wrote:

sir,
so you mean A-->B, B-->C then A-->C this part I do understand
but how can NOT C-->NOT A???
that is like saying, if floor is weet then it rained, if not rained then floor is not weet.

Yes sir, that's exactly correct: "If A, then C" also means "If NOT C, then NOT A."

If it rains it gets wet outside. Therefore, if it is NOT wet outside, then it has NOT rained.

If you are in Tokyo, then you are in Japan. Therefore, if you are NOT in Japan, then you are NOT in Tokyo.

If the car is running, then there is gas in the tank. Therefore, if there is NOT gas in the tank, then the car is NOT running.

If the people are at home, then the lights are on. Therefore, if the lights are NOT on, then the people are NOT home.

If A, then B. Therefore, if NOT B, then NOT A. (These are a pair of contraposing conditional statements; they are different ways of saying the same thing).

Isn't there a flaw for "If the people are at home, then the lights are on. Therefore, if the lights are NOT on, then the people are NOT home." Due to there can be people sleeping at home so the light is not on.

Second, how do I defined what A or B should be? I mean, in the "rain & wet" example. Don't they have different outcomes if I set "rain as A and wet as B" or "rain as B and wet as A

However, when I use my own world to explain in the following way: If I can make $20, then I can possibly make $40 as well. But if I can NOT make $40 doesn't mean that I can NOT make $20.

alan7858 wrote:Cool~~
I have clearly understand now.
Thank you so much to be so patient.
Really appreciate^^