52 | New Scientist | 16 November 2019
The back pages Puzzles
Quick crossword #45 Set by Richard Smyth Quick quiz #29 Puzzle set by Rob Eastaway
#30 Sticking in a PIN
Sachin tells me that the four-digit PIN that
he uses for his credit card has an unusual
property. When he enters his PIN into a
calculator and squares it, the last four
digits of the answer are also his PIN.
He tells me that exactly one of the digits
in his PIN is a zero, but he won’t tell me
which position it is in.What is Sachin’s PIN?Answer next week#29 How many strips?
Solution
It is possible to make 15 strips.To see why, number every position
(whether filled or not) in repeated patterns
of 1, 2, 3, 1, 2, 3, 1, 2 (next row) 3, 1, 2, 3, 1,
2, 3, 1 etc. In total there are 22 squares
labelled with a ‘1’.The way the numbers fall mean that every
plank must lie across a ‘1’, ‘2’ and ‘3’ space
horizontally or vertically. All seven holes
fall where the ‘1’ positions are, leaving
15 remaining 1s. This means you can
have only 15 strips. There are several ways
in which these strips can be cut out.1 What is the official
chemical name and
formula for baking soda?2 The apparently aberrant
brightness of distant type Ia
supernovae led astronomers
to infer the existence of
what mysterious entity
in the late 1990s?3 What is the name given
to the supercontinent that
made up most of Earth’s
landmass at the beginning
of the Neoproterozoic era
between 1.1 billion and
750 billion years ago?
4 Jonas Salk’s name
is associated with the
discovery of a vaccine
in the 1950s for what
debilitating disease?5 Giga, tera, peta, exa...
what comes next in the
list of orders of 1000?Answers belowCryptic
Crossword #18
AnswersACROSS 1 Sputnik, 5 Iotas,
8 Crescendo, 9 Lei, 10 Sable,
12 Trample, 13 Fluorocarbons,
15 Rubicon, 17 Sioux, 19 Gar,
20 Marsupial, 22 Sedge,
23 YardarmDOWN 1 Sacks, 2 Use,
3 Nuclear, 4 Kinetic energy,
5 Iboga, 6 Telephoto, 7 Swivels,
11 Blubbered, 13 Forages,
14 Rescuer, 16 Comte,
18 Xylem, 21 Ipahydrogen carbonate, Sodium 1NaHCO₃hatever it is, Dark energy. W 2it is causing the universe’sexpansion to accelerate,eaning distant supernovae mare fainter than expectedRodinia 3Polio 4Zetta. A zettabyte, for instance, 5or a thousand billion 21 is 10billion bytes
ACROSS
8 Half- (4)
9 Asian feline, Prionailurus
bengalensis (7, 3)
10 Quantity expressing the
ratio in which the length
of a vector is increased (6)
11 Long-legged bird in the
family Phoenicopteridae (8)
12 Red green blue alpha (4)
13 Arid(ish) habitat (10)
16 Pierre-Leon ___, author
of a theory in Euclidian
geometry (4)
17 Remove from packaging
(perhaps on YouTube) (5)
18 Stand-alone shell, in Unix (4)19 Two-terminal component
that uses the electron
tunnelling effect (5,5)
21 ___ Canal, shipping
waterway completed
in 1825 (4)
22 Tech billionaire; founder
of SpaceX (4,4)
26 ___ acid,
CH 3 CH(OH)CO 2 H (6)
27 Atmospheric layer
composed of
homogeneously
mixed gases (10)
28 Genus of succulents (4)Answers and the next cryptic crossword next week.
Correction: 13 across for cryptic crossword #16 was assay.DOWN
1 Propulsion devices such
as those developed by
Frank Whittle (3,7)
2 Sedimentary rock from
which liquid hydrocarbons
may be obtained (3,5)
3 Sonic waves of
frequencies >20kHz (10)
4 Architectural shelter (4)
5 National Aeronautics and
Space Administration (4)
6 Swirling motions,
in fluid dynamics (6)7 ___ Liwei, taikonaut (4)
14 Term for a Chicago-Florida
passenger train (5,5)
15 Rust-resistant
sheet metal (6,4)
18 Testa (4,4)
20 ___ the salmon, ribbonfish
of the eastern Pacific (4,2)
23 Bernard ___, French
astronomer (4)
24 Formerly, the
US Patent Office (4)
25 Leg joint (4)Get in touch
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AnswersEXAMPLE