Question

What percentage of numbers from 1 to 30 has 1 or 9 in the unit digit?

Answer 1

Hint – Write all the numbers which has 1 0r 9 in the unit’s digit and then to find the percentage of numbers, use the formula, ((Total numbers which has 1 or 9 in the unit’s digit)/30) * 100%.

Complete step-by-step solution -
We have been given numbers from 1 to 30.
So, numbers which have 1 or 9 in the unit's digit are 1, 9, 11, 19, 21, 29.
So, out of the 30 numbers, total 6 numbers have 1 or 9 in the unit’s digit.
Now, the percentage of numbers from 1 to 30 which has 1 or 9 in the unit digit is, N% = $\dfrac {\text {Total numbers which has 1 or 9 in the unit digit}}{{30}} \times 100 \% $
Therefore, $N\% = \dfrac{6}{{30}} \times 100\% = \dfrac{1}{5} \times 100\% = 20\% $.
Hence, the percentage of numbers from 1 to 30 which has 1 or 9 in the unit digit is 20%.

Note – Whenever such types of questions appear, first write the numbers from 1 to 30, then see which number has 1 or 9 in the unit digit, as here mentioned in the solution from 1 to 30, 1. 9, 11, 19, 21, 29 has 1 or 9 in the unit digit. So, a total of 6 numbers. Then find the percentage.