20points!!!percentage problems

Q1)

(a) A=(1+10%)B,
B=(1-10%)C ----[than]字之後係主角,從佢出發

so A=(1+10%)(1-10%)C
=1.1*0.9C
=0.99C
=(1-1%)C
so A is 1% less than C.


(b) A=0.99C
A/0.99=C
A*(1/0.99)=C

---->1/0.99=1.010101.......
=101.01% (corr. to 5 sig. fig.)
=1+1.01%

so A(1+1.01%)=C
C is 1.01% greater than A.


(c) New A =0.99C*(1+10%)
New B =0.9C*(1+10%)
New C =(1+10%)C

so A:B:C =0.99C*(1+10%) : 0.9C*(1+10%) : (1+10%)C

=0.99 : 0.9 : 1
=99 : 90 : 100

2015-03-22 13:36:53 補充：
Q31)
(a) horizontal line than vertical dotted line

(b) after the break, it is 1:00pm, so Tom drives for 2 hours to 3:00pm

average speed before the break
=50*2/3
=33.3km/h

average speed after the break
=50*5/(2+1+2)
=50km/h

so the % increase
=(50-33.3)/33.3*100%
=50%

2015-03-22 13:37:13 補充：
Q31)
(a) horizontal line than vertical dotted line

(b) after the break, it is 1:00pm, so Tom drives for 2 hours to 3:00pm

average speed before the break
=50*2/3
=33.3km/h

average speed after the break
=50*5/(2+1+2)
=50km/h

so the % increase
=(50-33.3)/33.3*100%
=50%

可惜~~ 可惜~~!!!