New Scientist - USA (2020-08-15)

54 | New Scientist | 15 August 2020

Puzzle

set by Chris Maslanka

#72 A long lane

The mathematician Professor

Numero lives at number 13 Long

Lane, the same road as his good

friend Professor Lemma, who is

at number 156. The friends like

that their house numbers when

multiplied together are exactly

divisible by the two numbers

added together. However,

Numero has always had his eye

on number 28, which he thinks is

“perfect”. “If only Lemma could

also move so that our houses

still had the same mathematical

relationship,” says Numero.

Bearing in mind that Long Lane

lives up to its name, what is

the biggest house number that

Lemma could move to?

Answer next week

#71 White lines

Solution

It requires a minimum of four lines to

link all white squares. The two white

corners (A and B) must be start/end

points because they touch only one

other white square. Start at A and

your first move is to C. The edge

square D will be stranded unless the

line from C goes into D. The same

logic follows around all edge squares

which gets you to B. This covers

14 white squares and effectively

reduces the problem to a new one

with a 6x6 chess board. The same

procedure with a new line reduces

the board to 4x4. A third line gives

a 2x2 board. The final two squares

are then covered by a fourth line.

Quick

quiz #64

Answers

1 Benzene. With the

chemical formula

C6H6, this constituent

of crude oil has a

central ring of six

carbon atoms

2 Electrical resistance

3 Legionnaires’

disease, so called

because the outbreak

occurred at a

convention of the

American Legion

4 The Ordovician,

which ran from

485.4 to 443.8

million years ago

5 Callisto, to

complete the list of

the four “Galilean”

moons of Jupiter first

observed in 1610

Twisteddoodles

for New Scientist

Tom Gauld

for New Scientist

The back pages

B

C

D A