Answer :
The simple way to calculate this is to divide the new number which the population increased to (the 150,000) by the original number (120,000), and multiply by 100 to give it as a percentage.
So, 100 x (150,000/120,000) = 125%.
So the new population is 125% the size of the original population, which means it increased by 25%.
So, 100 x (150,000/120,000) = 125%.
So the new population is 125% the size of the original population, which means it increased by 25%.