4. Yes, Zack is correct.
56 7
----- = -------
400 50
Think about it. If we multiply both the numerator and the denominator of the second fraction above by 8, we get the same fraction as the one on the left.
7 x 8 56
---------- = -------------
50 x 8 400
∴ Yes, Zack is correct.
5.
We must assume that out of 400 of 150, 000 , about 3 coins will have misprint.
So, we can solve now.
150 000 400 ↔ Think, number of coins divided by misprints.
------------- = -----------
x 3
This is called the rule of three.
(150 000 x 3) = 400
450 000 400x
------------- = ------------
400 400
1,125 = x
∴ We can predict that there will be 1, 125 misprints in a year.
