Step by step explanation I am bad at explaining things If we want to find The group with the youngest age , we have to find the mean. The mean , means that we add up all the numbers ( the age) ,then divide them with how much number you added . For example, we add the age of group A 9+10+10+10+10+10+10+10+15+15+15+15+15+15+15+15+17+17+17+17+17+17+17+17+19+19+19+19+19+19=449 Than Count how many people are in group A , group A have 30 people that the number you will be dividing So 449 divided by 30 is 14.966 That the average
The same go for group B 10+10+10+10+10+10+14+14+14+14+14+18+18+18+18+18+18+25+25+25+25+25+28+28+28+28+29+29+29+29=519
There 30 peoples in group B 519 divided by 30 is 19.7 So the Average of groupB is 19.7
Group a is 14.9 and group B is 19.7 Group A average is smaller than Group B that means ,The average of Group A is younger than Group B so the answer will be group a