See All: Motivation For Interview Preparation
A small riddle about big thinking
At first glance, it sounds like a bad joke or a trick meant to waste time.
5 + 5 + 5 = 550
Using just one line, validate this statement.
Anyone with basic arithmetic will immediately object.
It’s wrong. Plainly, obviously, mathematically wrong.
And that’s exactly where most people stop.
But this question isn’t about arithmetic. It never was.
The candidate’s first reaction: resistance
The candidate in the interview reacts the way most of us would:
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“This isn’t a mathematical statement.”
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“It’s not a computer-generated expression either.”
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“It’s literally impossible to solve.”
All of those statements are correct.
And yet, they miss the point.
The interviewer isn’t testing math.
They’re testing how you think when the rules aren’t clear.
A subtle shift: from solving to validating
Pressed to try anyway, the candidate does something interesting.
Instead of trying to force a solution, they reframe the problem.
They add a single line — not to make the equation true, but to make the logic valid:
5 + 5 + 5 ≠ 550
With one small stroke, the statement is now correct.
Is this what the panel originally had in mind?
Probably not.
Is it still a valid solution?
Absolutely.
This is the moment where reasoning matters more than correctness.
Why this answer is actually brilliant
From an interviewer's perspective, the candidate demonstrated something crucial:
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They questioned the assumptions of the problem
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They didn’t panic under ambiguity
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They reframed the objective instead of rejecting it outright
That’s lateral thinking in action.
In real-world work—engineering, data science, product design—the hardest problems rarely come with clean constraints. The ability to say “maybe we’re interpreting this wrong” is often more valuable than knowing the formula.
The “expected” solution (and the hidden trick)
After the discussion, the interviewer reveals another way to solve it.
Look closely at the symbols.
If you draw a slanted line through the first plus sign, it turns into a 4:
Suddenly, the equation works.
Most people are trained to see:
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standing lines
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sleeping lines
But slanted lines often escape perception.
That’s the trick.
The deeper lesson
This question isn’t about cleverness for its own sake. It highlights a fundamental idea:
Constraints are often softer than they appear.
Some people try to solve problems strictly inside the box.
Others step back and ask whether the box itself can move.
Competitive interviews, research problems, and real-life decision-making all reward the second group.
Final thought
When you encounter a problem that feels impossible, pause before rejecting it.
Ask yourself:
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Am I solving the problem, or just reacting to its presentation?
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What assumptions am I treating as fixed?
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Is there another way to interpret “one line”?
Sometimes, the smartest move isn’t to calculate faster —
it’s to see differently.
As always, think laterally.
And good luck.
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