PH10A: Introduction to Logic
Tutorial Worksheet 3
Prepare this worksheet for discussion in the tutorial during the week of February 20
I
Test for the validity of the following arguments.
1.
No coal tar derivatives are nourishing foods, because all artificial dyes are coal tar
derivatives and no artificial dyes are nourishing foods.
2.
Since animals can feel pain and all intelligent beings can feel pain, animals are
intelligent beings.
3.
All Jamaicans are patois speakers. Some Jamaicans are not English speakers. Therefore
some patois speakers are not English speakers.
4.
If you didn’t register for this course, then you will not be able to do the examination.
You won’t be able to do the examination. Therefore you didn’t register for this course.
5.
If the country’s roads are properly repaired, then there are fewer potholes. There are
more potholes. Therefore the country’s roads are not properly repaired.
6.
You will either have to speak the truth and hurt someone’s feelings or lie and
compromise your integrity. You will not lie and compromise your integrity. It means
that you will have to speak the truth and hurt someone’s feelings.
7.
No one who watches the news is uninterested in current affairs, so every political
science student watches the news, as anyone who is a political science student is
interested in current affairs.
8.
A foetus is either a person or a mere bundle of cells such as a mole or wart. Since we
don’t think of a foetus in the same way we do a wart, it must be a person.
II
Solve the following logic puzzles, bearing in mind the use of deductive
arguments such as modus ponens, modus tollens and disjunctive syllogism.i
1
Last year was an eventful one for Smith family, as all four of the Smith sisters
(Adele, Brandy, Enid and Lynn) got married. Each bride’s wedding took place
during a different season (from winter through fall), and each woman invited her
sisters and their respective grooms (Jay, Len, Luke and Ray) to be in each her
wedding party. Can you find the names of the bride and groom whose wedding took
place each season?
a. Enid didn’t marry Jay.
b. Enid’s wedding was immediately before Brandy’s which was immediately
Luke’s.
c. Lynn married Ray, but not during the winter.
2
The Trend triplets are fussy eaters, so Mrs. Trend finds herself preparing more than
one entrée and more than one side dish when dinnertime rolls around. Last evening,
each daughter (including Katarina) ate two vegetables (from among beans, broccoli,
carrots and squash), along with a different entrée (chicken nuggets, fish fingers or
sausage). From the clues below, can you match each girl with her two vegetables
and entrée?
a. No vegetable was consumed by all three girls; the broccoli and squash were eaten
by one girl each.
b. Emma ate the chicken nuggets, but she didn’t eat beans.
c. Xenia ate the squash, but she didn’t eat the fish fingers.
3 The starship Centrepiece is on a six year mission to study intelligent life on other
planets. From January through June of the mission’s first year, the crew of the
Centrepiece made contact with the people of a different, defining characteristic. From
this information and the clues below, can you determine the planet studied each
month and the characteristic of the people who live there?
a. The planet inhabited by the sorcerers (which isn’t Wijaka) was studied one month
before the one populated by the giants, which was contacted one month before the
planet Azlomo.
b. The planet Sadilu was studied one month before the planet inhabited by
insubstantial wraiths, which was studied one month before the planet inhabited by
cave people.
c. The planet Wijaka was visited at some point before the planet Mibelu, which was
visited one month before the planet of hive-dwellers.
d. The planet of merpeople, which wasn’t visited in January, was studied at some
point before the planet Drosmi.
i
These puzzles were taken from Dell Logic Puzzles (January 2005)