Thinking Skills: Critical Thinking and Problem Solving

316 Answers to assignments

actual distribution of the votes of the

lower candidates. The one who survives

could go on to receive Brown’s vote and

win, so four candidates can still win.

3    This is a problem where we need to work

backwards. If we look at each dish in

turn, we can find out its timing so that it

is ready at 7 p.m.

Chicken: 15 minutes rest after 2 hours

of cooking. Turn on oven 15 minutes

before starting to cook.

Rice: 15 minutes cooking after

30 minutes soaking.

Broccoli: 5 minutes cooking after

5 minutes preparation.

Sauce: 15 minutes cooking after

10 minutes preparation.

Working out each event time and

putting them in order, we have:

Turn on oven 4.30 p.m.

Put in chicken 4.45 p.m.

Soak rice 6.15 p.m.

Prepare sauce 6.35 p.m.

Cook rice 6.45 p.m.

Cook sauce 6.45 p.m.

Remove chicken from oven 6.45 p.m.

Prepare broccoli 6.50 p.m.

Cook broccoli 6.55 p.m.

Eat 7.00 p.m.

4    As the length of the shelves is 1.6 m, they

must be cut lengthwise from the sheet of

wood. The 1.2 m side-pieces can be cut

either way. This leaves only two reasonable

options. The left-hand one clearly leads to

the larger uncut rectangle (in area).

e    The answer is ten (note the difference

from 4a).The first eight you take out

could all be black. You would then need

to take out two more to get a blue pair.

3.2 How do we solve problems?

1    The efficiency (in km/litre) is distance

driven divided by petrol used. The

calculations may be approximated as

shown in brackets.

In order the cars are:

Riviera: 8 km/litre

Roamer: 8.8 km/litre (just under 9)

Stella: 9.375 km/litre (just under 10)

Montevideo: 12 km/litre

Carousel: 14.375 km/litre (over 14)

2    The object is to find how many

candidates still have a chance of

winning. We can do this by transferring

the votes from each candidate who

drops out to the next lowest. (This is

the maximum number of votes that

the second lowest-placed candidate

could receive after the withdrawal of the

bottom-placed candidate.) As the bottom

candidate is withdrawn each time, we

would then get the following results:

Original After first

withdrawal

After

second

withdrawal

Patel 323 323 323

Brown 211 211 211

Walshe 157 157 157

Ndelo 83 83 158

Macpherson 54 75

Gonzalez 21

At this stage, either Walshe or Ndelo

could be withdrawn, depending on the