There is no age standard for helmet sizes, A helmet is sized according to the circumference of the persons head. Taking a tailors tape measure, measure from the tip of one ear back to the tip of the ear, Then determine which helmet feels comfortable to the shape of the persons head, Make sure it's comfortable and does not move front to back or side to side. Listed below is a link to the size chart from the Bicycle Helmet Safety Institute.
most likely a small to medium.
that depends entirely on the size of the ATV, but no matter the size, a helmet should be worn at all times.
size 12 or 14
Should wear 7/8 or meduim
A 12-year old girl should wear a size 12/14. If the girl is tall, she may want to go up a size so things will fit better.
Girls 10/12
yes
an 11
Whatever shoes fits their feet.
10 year old girls are not really supposed to be wearing any kind of cup size.It's best to wear training bras or sports bras...But if a 10 year old were to wear a cup size it would probably be a 32AA...11,12 and further that's when you really start to wear a cup size.
There is no particular size for 15 year old girl's to wear. Every girl is different in size and therefore you should get measured. If you go into shops like Debenhams or La Senza, they will measure your size for free and make sure you are wearing the correct size of bra. i think any size will do if it works for ex) i know a 12 year old size c and another 20 size b
age has nothing to do with it it is all about wen u strted puberty.