 # Numpy - Mathematical Operations on NumPy Arrays - Addition and Subtraction

In this chapter, we will be discussing some mathematical operations related to NumPy arrays.

Most of the mathematical operations on NumPy arrays are element-wise operations. For example, the element at a particular index in one 2-D Numpy array gets added/subtracted/multiplied/etc. to the element at the same index in another 2- D NumPy array.

e.g.

``````import numpy as np
a = np.array([ 20, 30, 40, 50])
b = np.arange(4)
``````

Values of `b` will be

``````array([ 0, 1, 2, 3])

c = a + b

print(c)
``````

Output will be

``````array([ 20, 31, 42, 53] )
``````

Subtraction

Subtraction between two NumPy arrays is also element-wise.

e.g.

``````import numpy as np
d = np.array([ 20, 30, 40, 50])
e = np.arange(4)
``````

Values of `d` will be

``````array([ 0, 1, 2, 3])

f = d - e

print(f)
``````

Output will be

``````array([ 20, 29, 38, 47] )
``````
INSTRUCTIONS

(1) Import the required libraries

``````import numpy as np
``````

(2) Please create a NumPy array `a_arr` with values (60, 70, 80, 90)

``````a_arr = np.array(<< your code comes here>>)
b_arr = np.arange(4)
``````

Now, we have two NumPy arrays - `a_arr` and `b_arr`

(3) Add these two NumPy arrays (`a_arr` and `b_arr`), and store the result in a variable `c_arr`

``````<<your code comes here>> = a_arr  + b_arr
``````

(4) Print array `c_arr` to see its values

``````print(c_arr)
``````

Subtraction (element-wise)

(1) Please create a NumPy array `d_arr` with values (60, 70, 80, 90)

``````d_arr = np.array(<< your code comes here>>)
e_arr = np.arange(4)
``````

Now, we have two NumPy arrays - `d_arr` and `e_arr`

(2) Subtract NumPy array `e_arr` from array `d_arr`, and store the result in a variable called `f_arr`

``````<<your code comes here>> = d_arr  - e_arr
``````

(3) Print array `f_arr` to see its values

``````print(f_arr)
``````

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