Review Exercises

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Roy19
Date: 27 Jul 2009 14:45
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Review Exercises

Roy19 27 Jul 2009 14:45

Is this the right place to say that there is something wrong about them?

19. Which of the following cannot be used to test if a variable is any of 1, 2, 3, or 4?

1. If sum(A={1,2,3,4
2. If (A=int(A))(A>=1)(A<=4)
3. If A={1,2,3,4}
4. If A(int(A)=A)(A<5)

Answer:If A={1,2,3,4} because the If command does not work with lists.

The fourth one also says true if the variable is negative

23. True or False: The following is an alternative to using the and operator.

:If Anot(B

Answer:True. Remember that multiplication is implicitly done on the TI-83 calculators.

That's no AND operation to me… Or did they mean and operation between A and not(B)? If so a better question would be 'is the following a good alternative for 'If A And not(B' ?

Last edited on 27 Jul 2009 14:47 by Roy19 Show more

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Re: Review Exercises

jnesselr 27 Jul 2009 15:26

No, for 19, the first one, will do this:
It will say A is equal to {1,2,3,4} so that would return {0,1,0,0} if A was 2. Then, the sum command would take all of them, and sum them to be 1. Therefore t is true.

For 19, the second one, will do this:
If A is a fraction, that is 0, and therefore everything is zero and not true.
If A is not greater than or equal to one, that is zero, and everything is not true.
If A is not less than or equal to four, that is zero, and everything is not true.
If nothing turns to zero, e.g. A is not a fraction, it is greater than or equal to 1, and less than or equal to 4, it will work.

For 19, the third one, will do this:
It test A to {1,2,3,4}, so if A is 2, that is {0,1,0,0}, but If can't test lists.

For 19, the fourth one, will do this:
If A is a fraction, it is 0.
If it is less than 5, it is zero.
The author probably thought that something like "If -2" would return false, but apparently he was wrong. Maybe we should add that.

For 23, If you think about it as doing Not( first, this is it: So if B is anything other than 0, it is now 0, if it was 0, it's now 1. Let's say B was 0, and therefore turned to a 1. If A was a zero, that would be false. If A was 1, that would be a true. So, yes you are right. That actually follows this logic table: