Answer:
156 mm.
Explanation:
[tex]t_o[/tex] = Thickness of old coin before 1987 = 2.55 mm
[tex]t_n[/tex] = Thickness of new coin after 1988 = 1.75 mm
Number of coins of both types are 195 = n
Thickness of stack of old coins
[tex]s_o=n\times t_o\\\Rightarrow s_o=195\times 2.55\\\Rightarrow s_o=497.25\ \text{mm}[/tex]
Thickness of stack of new coins
[tex]s_n=n\times t_n\\\Rightarrow s_n=195\times 1.75\\\Rightarrow s_n=341.25\ \text{mm}[/tex]
Difference in the stack heights
[tex]\Delta s=s_o-s_n\\\Rightarrow \Delta s=497.25-341.25\\\Rightarrow \Delta s=156\ \text{mm}[/tex]
The new stack is 156 mm lower than the old stack of coins
The difference in the height of the stacks will be 156 mm.
