New Scientist - USA (2020-09-12)

54 | New Scientist | 12 September 2020

Puzzle

set by Zoe Mensch

#76 Four hippos

The rangers at the Savannah

Wilderness Experience are on

a mission to weigh the four

adult hippos in the park. Their

scales can bear a weight of up

to 4 tonnes, but are unreliable

with anything below 2 tonnes,

and all the hippos weigh less

than that, so the rangers have

had the smart idea of weighing

the hippos in pairs.

The first five weighings are:

2.23, 2.35, 2.48, 2.72 and

2.85 tonnes.

The rangers now guide the

two heaviest hippos onto the

scales, but as the weighing is

about to take place, the lightest

hippo sneaks on as well and the

scales break.

How much does the lightest

hippo weigh?

Answer next week

#75 Seventh time

lucky?

Solution

The code is 4321. Septa has four

correct digits in six goes. No digit

appears in a column more than

twice, so she has either got three of

the digits correct twice or two digits

correct twice and two once. The

digits that appear twice are: 7 in

the first column; 3 in the second

column; 2 in the third column; 8 in

the fourth column. The only pair of

these that doesn’t coincide is x 3 2 x.

One of the digits 4 8 8 2 is correct.

Since 2 can’t be repeated, it must

be 4, and from 1191, the last digit

must be 1.

Quick

quiz #68

Answers

1 Their beaks

2 In “magic”

mushrooms

3 It is cyclical –

expanding,

contracting and being

constantly reborn

4 Johannes Diderik

van der Waals

5 In autosomal-

dominant conditions,

you need only inherit

a mutated gene

from one parent; in

autosomal-recessive

conditions you

need to inherit a

mutated gene from

both parents

Twisteddoodles

for New Scientist

Tom Gauld

for New Scientist

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