Question
`120` identical spheres are arranged in the shape of a triangular pyramid. How many layers are there in the pyramid?
Note: This is a pyramid, which is a three-dimensional shape, and not a triangle in a plane.
Difficulty level (1 very easy - 10 very hard): 1
Topics:
Geometry
->
Solid Geometry / Geometry in Space
Arithmetic
Logic
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Reasoning / Logic
Proof and Example
->
Constructing an Example / Counterexample
Algebra
->
Sequences
->
Arithmetic Progression / Arithmetic Sequence
Algebra
->
Sequences
->
Complete/Continue the Sequence
Number Theory
->
Triangular Numbers
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