Question

A wooden ruler’s markings have worn out, and the only marks left are shown (in inches). How many integral inches between 1 and 12 cannot be measured directly with it?

• A. 0
• B. 1
• C. 2
• D. 3

Answer 1

The correct option is C 2

We have to go by trial and error method to solve this one.
To measure 1 inch
1 - 0 = 1
To measure 2 inches
3 - 1 = 2
To measure 3 inches
3 - 0 = 3
To measure 4 inches
7 - 3 = 4
To measure 5 inches
12 - 7 = 5
To measure 6 inches
7 - 1 = 6
To measure 7 inches
7 - 0 = 7
To measure 8 inches
$Notpossible$
To measure 9 inches
12 - 3 = 9
To measure 10 inches
$Notpossible$
To measure 11 inches
12 - 1 = 11
To measure 12 inches
12 - 0 = 12
Only 8 and 10 cannot be measured using this ruler.