Of the following, which is closest to the increase from 1975 to 1980 in the amount received by the processor in producing 6 ounces of frozen orange juice?
(A) $0.03
(B) $0.05
(C) $0.06
(D) $0.08
(E) $0.13
It looks like a cumbersome problem at first, but approximation can help here, if you use it well...
NOTE - we need to subtract 1980's value from 1975's value to find the difference
use 3 for 1975 instead of 0.3 AND
7 for 1980 instead of 0.7
so for 1975
31.7% is equivalent to a little less than 1/3 = 33/100
therefore 33% of 3 is 1 or a little less than that, lets say around 0.9
now, for 1980
18% of 7 is close to 20% of 7 and 20% is 1/5
so 1/5*7 is around 1.4 and if we calculate
1.4-0.9 = 0.5
and divide it by 10 to make up for the step we did to make our calculation easier.. - 0.05
but we know that we have rounded up.. so we need to pick an answer less than this value only (A) 0.03 is the one..
and yes, even if you, while calculating 1/5*7, could have rounded it down to lets say 1.2 or 1.3 which would have given you 0.03/0.04 .. to make sure that (A) is the right answer..