# What weight will the fourth scale display?

Credit: Brilliant.org

#### What weight will the fourth scale display?

Think carefully! There’s a quick and clever shortcut for solving this.

Correct!

Wrong!

Wrong!

Let

R, C, and D be the weights of the rabbit, cat, and dog, respectively. Each picture lends itself to an equation, giving us the following system:

R + C = 10,

D + R = 20,

C+ D = 24,

C + D + R = ?

If we add these equations together, we get

2C + 2R + 2D = 54.

If we divide by 2, we are left with the sum of the weights of each animal:

C + R + D = 27.