Alex runs up a staircase with n steps, and can hop either 1, 2, or 3 steps at a time. Count how many possible ways the child can run up the stairs. solution?

There are 4 possible ways

Step-by-step explanation:

Data provided in the question:

Alex can hop in 1 steps, 2 steps, or 3 steps at a time.

From the above data it can be concluded that at a single maximum 3 steps can be run at a time

thus,

for running 3 steps at a time from the above data, we can have

with 1 step only : {1, 1, 1}

with 1 step first and 2 steps : {1, 2}

with 2 steps first and then the 1 step: {2, 1}

and 3 steps at once : {3}

thus, we have 4 possible ways to run up the stairs keeping the above condition.