# Challenge Questions

Stop in and exercise your brain. Talk about this month's Challenge from Specs & Techs or similar puzzles.

So do you have a Challenge Question that could stump the community? Then submit the question with the "correct" answer and we'll post it. If it's really good, we may even roll it up to Specs & Techs. You'll be famous!

Answers to Challenge Questions appear by the last Tuesday of the month.

# Two Trains, a Bird and Crash (Sept. 2021 Challenge Question)

Posted August 31, 2021 12:00 AM
Pathfinder Tags: challenge question

It's 1870 and the Transcontinental Railroad has just been completed.

A Central Pacific steam locomotive leaves San Francisco at 15 miles per hour at 3 p.m., September 1, heading east.

A Union Pacific steam locomotive leaves New York City at 20 miles per hour at 3 p.m., September 1, heading west.

The length of track between the two stations is approximately 3,500 miles. The trains do not make any stops along the way.

At 3 p.m., September 1, a bird leaves New York City, following the tracks, at 25 miles per hour. It flies until it reaches the eastbound train, when it instantly reverses direction.

When it reaches the westbound train, the bird reverses course again, and flies back to the eastbound train. The cycle repeats until the bird is killed in a fiery, catastrophic train wreck.

How many miles did the bird fly? When do the trains collide? (Be specific!)

85 comments; last comment on 09/04/2021

# Broken Billiard Balls (August 2021 Challenge Question)

Posted July 31, 2021 12:00 AM
Pathfinder Tags: challenge question

You are the proud owner of eight billiard balls. You believe one of them is defective, and weighs more than the others.

You are also the proud owner of a balance. It tells you what pan is heavier, but not the measured weight.

What is the smallest number of weighings required to find the defective ball? How do you do it?

33 comments; last comment on 09/01/2021

# A suspicious suitcase and a boat (July 2021 Challenge Question)

Posted June 30, 2021 12:00 AM
Pathfinder Tags: challenge question

Say you are on a fishing boat on a medium-sized lake with a suspicious 5 lb suitcase. For reasons unknown, you decide to throw the suitcase overboard.

Does this cause the lake’s water level to rise or fall, or is there no change?

What if you were to tie the suitcase to a fishing line?

For buoyant items, displacement depends on weight.

If the suitcase floats, it has no effect on the water level.

If the suitcase sinks, the water level will fall.

If the suitcase is suspended by a line, it has no effect on the water level.

27 comments; last comment on 07/26/2021

# Which Light Switch?

Posted May 31, 2021 12:00 AM
Pathfinder Tags: challenge question

Here's a brain teaser for the electricians out there.

A lightbulb is behind a closed closet door - you cannot see it. It is currently off.

There are three identical wall switches outside the closet, labeled A, B and C.

You need to determine which switch operates the lightbulb. You can open the door exactly once.

How do you do so?

16 comments; last comment on 08/28/2021

# Missing Operators: May 2021 Challenge Question

Posted April 30, 2021 12:00 AM
Pathfinder Tags: challenge question

Make this equation true. Do so by inserting mathematical operators between any digits. Multiple answers may be correct (we know of at least one).

Eligible Operators: + - × ÷ ()

EQUATION

1990 = 999999999999999

8 comments; last comment on 05/21/2021