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? 



Answers (1)

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.