Alex Bellos - Perilous Problems for Puzzle Lovers

Tasty teasers

Grueling grids

What is the smallest number of straight lines you need to draw across a 3 3 grid so that every cell in the grid has at least one of the lines passing through it? The answer is fewer than three. Draw your solution.

What is the smallest number of straight lines you need to draw across a 4 4 grid so that every cell in the grid has at least one of the lines passing through it? The answer is fewer than four. Draw your solution.

Place five stones on the 8 8 grid shown below in such a way that every square consisting of nine cells has only one stone on it

The remaining questions all ask you to draw a pattern on a grid of 16 dots, shown below.

A polygon is a shape in which each side is a straight line. The H polygon below has 12 sides and the K has 13. Draw a polygon on the grid with 16 sides. (Note: Each side of the polygon must join two dots. Lines cannot overlap. The shape, which need not resemble a letter, must have no gaps in its outline, and each dot can be passed through at most once.)

Below is a single square made by joining four dots in the grid. Find the other 19 squares that can be made by joining four dots. (Lines connecting the four dots may pass through other dots.)

The illustration below shows a way to connect 14 of the dots with lines, such that the angle at every dot is acute (i.e., less than 90 degrees). Find a way to connect all 16 dots so that there is an acute angle at every dot.

Tasty teasers

Riotous riddles

Each of these puzzles relies on the solvers making a mistaken assumption at first.

Two identical children born on the same day to the same mother and father are not twins.

How is this possible?

A certain man had great grandchildren, yet none of his grandchildren had any children.

How is this possible?

You are on a plane, a mile above sea level. Huge mountains lie directly ahead. The pilot does not change his course, speed, or elevation. Yet you survive.

How is this possible?

A woman has a bucket of water in her hands. She turns it upside down, but the bucket stays full. There is no bucket lid, the water is in liquid form, and she is not relying on centrifugal force.

How is this possible?

A clean-shaven teenager told his parents he was going to a party, and would be back before sunrise. He got back before sunrise, and had a fully-grown beard!

How is this possible?

A boxer left a contest victorious, winning the national championship. Even though his trainer took all the money, the boxer was quite happy.

How is this possible?

Identical twins Milly and Molly always wear the same clothes. One day I saw one of them and I shouted hello. As soon as she turned to me I knew it was Milly.

How is this possible?

A woman working in an office is fired from her job. The following day she shows up at the same office, where she is welcomed.

How is this possible?

My neighbor is 92 years old and frail. One day I invited her over to do something I was not able to do. She was able to carry out the task, even though she has no skills that I do not have.

How is this possible?

One day a man saw the sun rise in the west.

How is this possible?

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ALSO BY ALEX BELLOS

Can You Solve My Problems?

Puzzle Ninja

Heres Looking at Euclid

The Grapes of Math

Futebol: The Brazilian Way of Life

BY ALEX BELLOS AND EDMUND HARRISS

Patterns of the Universe:A Coloring Adventure in Math and Beauty

Visions of the Universe: A Coloring Journey through Maths Great Mysteries

PERILOUS PROBLEMS FOR PUZZLE LOVERS: Math, Logic & Word Puzzles to Challenge Your Brain
Copyright 2019, 2020 by Alex Bellos

Originally published in Great Britain as So You Think Youve Got Problems? by Guardian Books/Faber and Faber Ltd in 2019. First published in North America in revised form by The Experiment, LLC, in 2020.

All rights reserved. Except for brief passages quoted in newspaper, magazine, radio, television, or online reviews, no portion of this book may be reproduced, distributed, or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or information storage or retrieval system, without the prior written permission of the publisher.

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Library of Congress Cataloging-in-Publication Data

Names: Bellos, Alex, 1969- author.
Title: Perilous problems for puzzle lovers : math, logic, & word puzzles to
challenge your brain / Alex Bellos.
Description: New York : The Experiment, 2020. | Originally published in
Great Britain as So You Think You've Got Problems? by Guardian
Books/Faber and Faber Ltd in 2019.
Identifiers: LCCN 2020037429 (print) | LCCN 2020037430 (ebook) | ISBN
9781615197187 (paperback) | ISBN 9781615197194 (ebook)
Subjects: LCSH: Mathematical recreations. | Puzzles.
Classification: LCC QA95 .B4416 2020 (print) | LCC QA95 (ebook) | DDC
793.74--dc23
LC record available at https://lccn.loc.gov/2020037429
LC ebook record available at https://lccn.loc.gov/2020037430

ISBN 978-1-61519-718-7
Ebook ISBN 978-1-61519-719-4

Cover and additional text design by Jack Dunnington
Text design by carrdesignstudio.com
Illustrations by Andri Johannsson