Dictionary-of-cubes.md

9.2: Cube Sum

The Problem

With a given integral number n, write a program to calculate the sum of cubes.

Hints

Cubes mean power of 3. Hence, the cube of 9 is 9**3.

Here you have to calculate the cube of a series. If you want to calculate the cube up to the number n. The series will look like-

1^3+2^3+3^3+4^3+ .. .. .. +n^3

If you remembered the sum of the square, this one will be easier for you.

The solution

def cube_sum(num):
	sum = 0
	for n in range(num+1):
		sum = sum + n**3
	return sum


user_num = int(input('Enter a number: '))
result = cube_sum(user_num)
print('Your sum of cubes are: ', result)

Try it on Programming Hero

Think Different

There is an alternative solution to calculate the sum of cube of the n numbers. You can use

(n*(n+1)/2)^2

Alternative Solution

n = int(input('Enter a number: '))
sum = (n*(n+1)/2)**2
print('Your sum of cubes are: ', sum)

Try it on Programming Hero

Take Away

Sum of a series might have an easier formula.

   

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