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 hour to
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
hours; 30% helped for
hour to
hours; 50% did not help at all.
Using this, answer the following :
(i) How many parents were surveyed?
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Let the number of parents surveyed be X.
30% of them helped for for
hour to 
hours.
In total, there were 90 such parents.
Therefore, There were total of 300 parents who were surveyed.