✓ Question 13: 2 kg
If 3 cats catch 3 mice in 3 minutes, how many cats catch 100 mice in 100 minutes?
Why, in question 13: A brick weighs 1 kg plus half a brick. How much does the whole brick weigh?
The answer is 2 kg. If the brick weighs 1 kg plus half a brick, the other half of it weighs 1 kg. The two halves together weigh 2 kg.
Set up a simple equation
Option 1.5 kg is the most chosen, because it seems to add 1 kg to half of 1 kg. But the half brick in the statement is half of the real brick, whose weight we don't yet know.
Written as a calculation, it's clearer: the brick equals 1 kg plus half of itself. Taking that half away from both sides, half a brick weighs 1 kg.
If half a brick weighs 1 kg, the whole brick weighs double, 2 kg. You can check: 1 kg plus half a brick, which is 1 kg, gives exactly 2 kg.
Puzzles of this kind have appeared in puzzle books for a long time, always with the same idea: the missing value appears on both sides of the equation.
