# import necessary libraries
import pandas as pd
import numpy as np

# define your series
my_series = pd.Series([10,20,30,40,50,60,70,80,90])

# use np.percentile() method
percentile_25 = np.percentile(my_series, 25)
percentile_75 = np.percentile(my_series, 75)

# print results
print(f'25th Percentile is: {percentile_25}')
print(f'75th Percentile is: {percentile_75}')