Can you solve the death race riddle? - Alex Gendler
The night before the Death Race
across the Wastelands is set to begin,
your uncle,
the great inventor Slate Kanoli,
got kidnapped
by the ruthless No-Side gang.
The only way to get him back
is to race his Coil Runner
against the gang yourself.
Win and they’ll give back your uncle.
Lose and you’ll forfeit the Coil Runner
and all his other creations.
As the grueling race gets underway,
you find yourself falling further
and further behind.
Your only chance is to take a shortcut
your uncle told you about––
the Flux Ravine gambit.
Fortunately, the Coil Runner comes
equipped with emergency turbo thrusters.
Unfortunately, your uncle
was a notorious tinkerer,
and the system still had some kinks
to work out.
Just minor things
like the ignition exploding,
the reactor leaking,
or the oxygen levels depleting—
any of which would end
your racing career immediately.
Before his kidnapping,
Uncle Slate determined
that each of these critical failures
was the ultimate result
of a chain reaction
originating in the thrusters.
He was also certain that while one factor
could trigger two different effects,
and two factors could each independently
lead to the same effect,
no effect is caused by two factors
in conjunction.
However, Uncle Slate
never got around to pinpointing
which thruster was responsible
for which error.
All you have
are the notes from his test runs:
1. When thrusters B and C are on,
the Fuel gauge glows.
2. When thrusters A, B, and D are on,
the Fuel gauge glows
and the Helium tank rattles.
3. When thrusters C, D, and E are on,
the Fuel gauge glows
and the Gravitometer spins.
4. When thrusters A, D, and E are on,
the Gravitometer spins
and the Helium tank rattles.
5. Shortly after the Helium tank rattles
and the Gravitometer spins,
the Ignition explodes
and the Oxygen levels deplete.
6. Shortly after the Fuel gauge glows
and the Gravitometer spins,
the Reactor leaks.
You need to use
as many thrusters as possible
to give yourself the best chance
at clearing the gap,
without triggering any of the three
catastrophic failures.
Which thrusters should you activate?
Answer in 3
Answer in 2
Answer in 1
The most important thing
to remember here
is that even if we know
that one thing causes another,
the converse is not necessarily true.
For example, this panic switch
shuts off the coil runner’s engine.
But the engine being off
doesn’t necessarily mean
the panic switch was engaged—
the coil runner could be
out of fuel, or damaged—
or turned off normally.
We can, however,
conclude that if the engine is running,
the panic switch hasn’t been engaged.
With that in mind, one way we can start
is to work backwards
from the three defects that could
knock you out of the race.
So let’s look at Slate’s last two notes,
since they give direct information
about those.
The Gravitometer spins in both cases,
but the results are different.
That means the spinning Gravitometer
can’t be the cause
of any particular malfunction.
If it were, the same thing would happen
each time.
So we can conclude that a glowing
Fuel gauge makes the reactor leak,
while a rattling Helium tank
makes the Ignition explode
and depletes the Oxygen levels.
Once we know which two errors
we need to avoid,
we can make a table
and use the logic of cause and effect
to see which thrusters trigger them.
Since the Helium tank is fine
during the first test run
when thrusters B and C are active,
we can assume neither makes it rattle.
And from the third run
we know that D and E don’t either.
That leaves thruster A,
which was indeed used
in the second and fourth test runs
where the Helium tank rattled.
Now what causes the glowing Fuel gauge?
From the fourth test run we know
it can’t be thrusters A, D, or E.
So is the culprit, B, C,
or each of them separately?
The answer can be found
in the second and third test runs:
the fuel tank glowed in both,
but B was activated in one,
and C in the other.
That means the B and C thrusters each
independently make the Fuel tank glow.
It looks like the A, B, and C
thrusters are off limits.
Fortunately, the other two
are just enough to clear the jump.
You rocket into first place
and the gang
begrudgingly hands over your uncle.
He thanks you profusely,
and decides to celebrate your victory
with a cup of tea
from his latest contraption...
