If Ian uses 1/20 of the ketchup 4 times, this is equal to 4/20, or [tex] \frac{4}{20} [/tex].
[tex] \frac{4}{20} [/tex] can be simplified to [tex] \frac{1}{5} [/tex], which means we need to work out [tex] \frac{1}{5} [/tex] of 12.2
[tex] \frac{1}{5} [/tex] is equivalent to 20%, which as a decimal is 0.2
0.2 x 12.2 = 2.44 - however, this is how much he has used, and we need to figure out how much is left.
12.2 - 2.44 = 9.76
So, Ian has 9.76 oz remaining :)
