# Help Zone

### Student Question

Secondary IV • 1yr.

Express the average of three sister in term A of the first born in years, if the second was born 5years after the first and the third was born 5 after the second.

Mathematics

## Explanations (2)

• Options
1yr.

The average age of the three sisters

F being the age of the first born;

S being the age of the seconde born and S = F + 5;

T being the age of the third born and T = S + 5 = F + 10;

The average age of the three sisters = (F + S + T)/3

And you can express the average age of the three sisters in term of the first born by substitution.

• Explanation verified by Alloprof

Explanation verified by Alloprof

This Explanation was verified by a member of the Alloprof team.

Options
Help Zone Pro • 1yr.

Hello TalkativeMercury6660,

This is what we know :

First born = a

Second born = a-5

Third born = a-5-5

Now, to calculate the average, you need to find the sum of the age of the three siblings and divide them by 3.

I hope my explanation helped you, good luck :)

Laura Cristina