NumPy: Sum of all the multiples of 3 or 5 below 100

Last update on August 29 2025 12:50:18 (UTC/GMT +8 hours)

Sum Multiples of 3 or 5 Below 100

Write a NumPy program (using numpy) to sum all the multiples of 3 or 5 below 100.

Pictorial Presentation:

Python NumPy: Create a vector of size 10 with values ranging from 0 to 1, both excluded

Sample Solution:

Python Code:

# Importing the NumPy library and aliasing it as 'np'
import numpy as np

# Creating an array 'x' using NumPy's arange function,
# generating values from 1 to 99 (inclusive) since the end value is exclusive
x = np.arange(1, 100)

# Finding numbers in the array 'x' that are multiples of 3 or 5
n = x[(x % 3 == 0) | (x % 5 == 0)]

# Printing the first 1000 elements of the array 'n'
print(n[:1000])

# Printing the sum of the numbers in the array 'n'
print(n.sum())

Sample Output:

[ 3  5  6  9 10 12 15 18 20 21 24 25 27 30 33 35 36 39 40 42 45 48 50 5
1 54                                                                   
 55 57 60 63 65 66 69 70 72 75 78 80 81 84 85 87 90 93 95 96 99]       
2318

Explanation:

In the above exercise –

‘x = np.arange(1, 100)’ creates a 1D NumPy array with integers from 1 to 99 and stores it in the variable ‘x’.

n = x[(x % 3 == 0) | (x % 5 == 0)]: This line creates a boolean mask for elements in ‘x’ that are divisible by 3 or 5. The % operator computes the remainder of the division, and == 0 checks if the remainder is 0. The | operator is a boolean OR, which combines the two conditions. The resulting mask is then used to index ‘x’, creating a new array ‘n’ containing the numbers divisible by either 3 or 5.

print(n[:1000]): This part prints the first 1000 elements of the n array. Since there are fewer than 1000 elements in n, this will print all elements in the array.

print(n.sum()): This part calculates the sum of all elements in the n array and prints the result.

For more Practice: Solve these Related Problems:

Write a NumPy program to identify and sum all multiples of 3 or 5 below 100 using vectorized operations.
Create a function that filters multiples of 3 or 5 from an array and computes their total sum.
Compare the performance of summing multiples using np.where and np.sum versus a loop-based approach.
Test the solution by verifying both the list of multiples and the computed sum against expected values.

Go to:

PREV : Make Array Read-Only
NEXT : Create Array with 10^3 Elements

Python-Numpy Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.