F.1 maths. question (percentage)

1. Find the percentage increase or decrease .
a 15 increases to 20
the percentage increase
=(20-15)/15*100%
=33.3%

b. 16 decreases to 10
the percentage decrease .
=(16-10)/16*100%
=37.5%

c. 60 increases by 20
the percentage increase
=(20/60)*100%
=33.3%

d. 80 decreases by 20
the percentage decrease .
=(20/80)*100%
=25%

2. Find the new values after the changes.
a. 120 increases by 20% then decreases by 20%
the new values
=120(1+20%)(1-20%)
=120(1.2)(0.8)
=115.2

b. 96 decreases by50% then increases by 30%
the new values
=96(1-50%)(1+30%)
=96(0.5)(1.3)
=62.4


2007-12-10 20:14:27 補充：
the percentage change=(new value-original value)/original value*100%

1.Find the percentage increase or decrease .
15 increases to 20
(20-15)/15*100%
=(500/15)%
=increase (33 1/3)%
16 decreases to 10
(16-10)/16*100%
= (600/16)%
=decrease 37.5%
c. 60 increases by 20
=20/60*100%
=200/6%
=(33 1/3)%
= increases (66 2/3)%
d. 80 decreases by 20
=20/80*100%
=200/8%
=25%
= decrease 25%
2. Find the new values after the changes.
a.120 increases by 20% then decreases by 20%
120*(1+20%)*(1-20*)
=120*120/100*80/100
=12*12*8/10
=115.2
b.96 decreases by50% then increases by 30%
96*(1-50%)*(1+30%)
=96*50%*130%
=48*13/10
=62.4

1a) percentage increase is
(20-15)/15 X 100%
=33 1/3% 百分之 三十三又三分一

1b) percentage decrease is
(16-10)/16 x100%
=25%

1c) percentage increase is
20/60 x100%
=33 1/3% 百分之 三十三又三分一

1d) percentage decrease is
20/80 x 100%
=25%

2a) 120 x (1+20%) x (1-20%)
=115.2

2b) 96 x (1-50%) x (1+30%)
=62.4

1a)33又1/3%
1b)37.5%
1c)33又1/3%
1d)25%

2a)115.2
2b)62.4