percentage(百分數) 既問題

1.A is 20% more than B,what percentage of A is B ?
Let B be x
A is 20% more than B, then A=(1+20%)x=1.2x
what percentage of A is B : (x/1.2x)*100%=83.3% (corr . to 3 sig. fig.)
2.A sum of money is evenly distributed to 15 people.If the amount remains unchanged,but the number of people is increased by 20%,find the percentage decrease of the amount each one recives.
Let the sum of money be $x
the original money of each one receives=$(x/15)
the number of people is increased by 20% ,
then the number=15(1+20%)=18
Thus, the new money of each one receives=$(x/18)
the percentage decrease of the amount each one recives
={[(x/15)-(x/18)]/(x/15)}*100%
=[(1/90)/(1/15)]*100%
=16.7%(corr . to 3 sig. fig.)

1.let's say a =1.2b, then b = a/1.2 = 83.33% a

2. first, everyone gets 1/15 sum, if increases to 18 people (20%), then everyone will gets 1/18 sum. the decrease in percentage = (1/15-1/18)/(1/15) = 16.67%