In a school of 260 children, 55% are girls. how many girls are there? at the same school, 10% of children leave for a school trip. how many pupils go on the trip?

Number of children in a school = 260
Percentage of girls in the school = 55%
Number of girls in the school = (55/100) * 260
                                                = 14300/100
                                                 = 143
So there were 143 girls in the school among 260 children
Percentage of children going for the school trip = 10%
Then
Number of students going for the school trip = (10/100) * 260
                                                                        = 26
So 26 children are going for the school trip. I hope the procedure is clear enough for you to face similar problems in future.

260 children* (55/100)= 143 students.
There are 143 girls~

260 children* (10/100)= 26 students.
26 students go on the trip~

Hope this helps~