The two equal-arm scales shown are balanced.
Of the following, 
has the same mass as
CEMC Gauss (Grade 8), 2019
Solutions — 2
Solution 1
The first scale shows that 
has the same mass as 
.
The second scale shows that 
has the same mass as 
.
Therefore, the sum of the masses of 
and 
is equal to the sum of the masses of 
and 
.
That is, the equal-arm scale shown below is balanced.
The left and right sides of this scale each contain a 
, and the scale remains balanced if one 
is removed from each side of the scale (since they are equal in mass).
That is, the equal-arm scale shown below is balanced.
Therefore of the answers given, 
has the same mass as 
.
Solution 2
On the spinner given, the prime numbers that are odd are and 7.
Since the spinner is divided into 8 equal sections, the probability that the arrow stops in a section containing a prime number that is odd is .
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