In a primary school, the parents were asked the number of hours they spend per day in helping their children to do homework. There were 90 parents who helped $\frac{1}{2}$ hour to $1\frac{1}{2}$hours. The distribution of parents according to the time for which they said they helped is given in the adjoining figure; 20% helped for more than $1\frac{1}{2}$  hours; 30% helped for   $\frac{1}{2}$  hour to $1\frac{1}{2}$   hours; 50% did not help at all. Using this, answer the following :(i) How many parents were surveyed?

Let the number of parents surveyed be X.

30% of them helped for for   $\frac{1}{2}$  hour to $1\frac{1}{2}$   hours.

In total, there were 90 such parents.

$\therefore$ 30% of X = 90

$\Rightarrow \frac{30}{100}\times X = 90 \\ \Rightarrow X = 90\times100 /30 = 300$

Therefore, There were total of 300 parents who were surveyed.

Exams
Articles
Questions