Try a Sample Logical Reasoning Question: Necessary Assumption

Test J, Section 3, Question 17

When exercising the muscles in one’s back, it is important, in order to maintain a healthy back, to exercise the muscles on opposite sides of the spine equally. After all, balanced muscle development is needed to maintain a healthy back, since the muscles on opposite sides of the spine must pull equally in opposing directions to keep the back in proper alignment and protect the spine.


Which one of the following is an assumption required by the argument?


A

Muscles on opposite sides of the spine that are equally well developed will be enough to keep the back in proper alignment.

B

Exercising the muscles on opposite sides of the spine unequally tends to lead to unbalanced muscle development.

C

Provided that one exercises the muscles on opposite sides of the spine equally, one will have a generally healthy back.

D

If the muscles on opposite sides of the spine are exercised unequally, one’s back will be irreparably damaged.

E

One should exercise daily to ensure that the muscles on opposite sides of the spine keep the back in proper alignment.

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So, the argument says that exercising opposite sides of the back equally is important to maintain a healthy back because balanced muscle development is needed to maintain a healthy back. This argument requires, “Exercising opposite sides of the back unequally will lead to unbalanced muscle development” to connect the two premises together.

A. This confuses sufficient for necessary. The argument says you need to develop muscles on both sides equally to maintain a healthy back, but it doesn’t say that’s all you need to do for a healthy back. Someone could have equally well-developed muscles but have poor posture or something that leads to an unhealthy back.

B. This is exactly what we’re looking for. Put into the original argument, and it reads as such, “Exercising opposite sides of the back equally is important because exercising them unequally leads to unbalanced muscle development.” And balanced muscle development is needed to maintain a healthy back.

C. This is wrong for the same reason as A. Proper muscle development is necessary for a healthy back, but the argument never says that this will guarantee a healthy back. It says if you don’t have balanced muscles, you won’t have a healthy back. This doesn’t mean if you do have balanced muscles, you will have a healthy back. Other factors can affect the health of your spine.

D. Woah, the argument never says anything about irreparable damage. The argument doesn’t need this.

E. Again, the argument doesn’t say anything about daily exercise. It doesn’t even say that you should exercise to get a healthy back, just that when you do exercise, do it equally.

The answer is B.

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