Question

What is 90 % of 80 ?

Answer 1

Hint: To calculate 90 % of 80, we should use the definition of percentage, i.e., specific kind of values per 100 values. Then, we will need to use the unitary method technique to find the required value. From a set of 100 values, we are interested in 90 of them. So, from 80 values, we will need $\dfrac{90}{100}\times 80$. Thus, we will get the required answer.

Complete step-by-step solution:
We are very well aware that the word ‘percentage’ is made up of a combination of 2 words, ‘per’, which means ‘for every’, and ‘cent’, which is equivalent to the number 100. So we can say that, percentage refers to the number of specific values per hundred values.
In our problem, we need to find 90 % of 80.
According to the definition of percentage, 90 % means 90 out of 100.
We can rephrase this as,
From 100, we need = 90
So, by using unitary method, we can say that
From 1, we need = $\dfrac{90}{100}$
And thus,
From 80, we need = \[\dfrac{90}{100}\times 80=72\].
Alternatively, we can directly use the following formula.
It is clear that to find A% of B, we can write A% of B = $\dfrac{A}{100}\times B$
Now, using this formula to solve our problem, we get
90 % of 80 = $\dfrac{90}{100}\times 80$.
Thus, 90 % of 80 = \[9\times 8=72\]
Hence, 90 % of 80 is 72.

Note: We should understand the concepts of unitary method to solve this problem. Alternatively, we can use the direct formula to solve this problem, which can be written as, A% of B = $\dfrac{A}{100}\times B$. We must take care not to write it as $\dfrac{90}{80}\times 100$ which will give a totally wrong answer.