Thinking Skills: Critical Thinking and Problem Solving

320 Answers to assignments

both an orange and a dollar must be

worth less than a grapefruit).

•   We can say nothing about the value of

a lemon relative to a grapefruit.

4    The information we have directly is:

Mon Tue Wed Thu Fri Sat Sun

L x x

M Y x Y x x Y Y

N x x Y

O Y Y

(We are given Moses’ three days off, so he

must work the other four. Liam is off on

Saturday, so the other three work).

From the table, we can see that Liam

and Orla must work on Friday.

Orla can then not work Wednesday

or Sunday or she would work four

consecutive days.

Therefore, Liam and Nadila must work

on Sunday and Liam on Wednesday. We

can fill in the table as far as shown below.

Mon Tue Wed Thu Fri Sat Sun

L x Y Y x Y

M Y x Y x x Y Y

N x x Y Y

O x Y Y Y x

We can now see that Nadila cannot work

both Monday and Tuesday or it would be

four in a row, so she must work Thursday,

and Liam must work Tuesday. This leaves

the only remaining flexibility that

Nadila and Orla must each work one of

The overall effectiveness will be the sum

of the first graph and that for drug B. It

will appear as in the second graph.

Average eectiveness

1

10

Time

Overall

The sizes and positions of the peak and

dip will depend on the exact values for

the original two curves.

2    Whilst this could be solved with a Venn

or Carroll diagram, the problem is simple

enough not to require either. Since

the percentages studying French and

German add to 115%, there must be at

least a 15% overlap so D is true.

Looking at the alternatives:

A It is possible that the 30% not

studying French are also part of the

55% not studying German.

B There is no reason to assume that^23 of

those who study German (30% of all

students) coincide with the 30% who do

not study French.

C This comes from subtracting the 45

from the 70. This number has no

meaning other than being the

maximum percentage who could

study French but not German.

3    C is the correct answer. The only firm

deductions that can be made are:

•   A dollar has a value between that

of an orange and a lemon (but it is

impossible to tell which is higher and

which is lower, so neither A nor D can

be correct).

•   The value of a grapefruit is one orange

plus one dollar (so C is correct and