How many siblings?

Algebra Level 2

Henry and Alice are siblings.
Henry has twice as many sisters as brothers.
Alice has the same number of brothers as sisters.

How many siblings are there all together (including Henry and Alice)?

Note: Henry is a boy, and Alice is a girl.

3 4 5 6 7

1 solution

Geoff Pilling
Dec 14, 2016

Let $G$ be the number of girls and $B$ be the number of boys.

Henry has $B-1$ brothers and $G$ sisters. So,

$G = 2 \cdot (B-1)$

Alice has $G-1$ sisters and $B$ brothers. So,

$B = G-1$

Solving,

$B=3$ and $G = 4$

$3+4 = \boxed7$