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Tuesday, August 22 2017 @ 01:37 PM CDT
 Forum Index >  Test Paper Related >  Primary 6 Matters
 Help on 2 maths questions
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By: Kuro (offline)  Sunday, August 24 2014 @ 03:03 AM CDT (Read 1508 times)  
Kuro

Q1. Refer to attachment.

Q2. Charen, Ella and Sharon took part in a 200-metre race. All the girls were travelling at a constant speed throughout the race and each girl's speed was different. When Charen completed the race, Ella and Sharon were 40m and 60m away from the finishing line respectively. How far was Sharon from the finishing line when Ella finished the race?

No answer keys. Thanks.

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By: echeewh (offline)  Monday, August 25 2014 @ 02:50 AM CDT  
echeewh

Hey <Kuro>

Following is my worked solution for Q2.

<---------------------- 200 --------------------------->
|---------------------------------------------------------|
|-> ********************************************* |->
C ********************************************** C1
s(C)
************************************* <--- 40 --->
|-> ********************************* |-> ******* |->
E ********************************** E1 ******* E2
s(E)
********************************** <----- 60 ----->
|-> ****************************** |-> ***** |->
S ******************************* S1 ***** S2
s(S)

By the time C completed race,
t(CC1) = t(EE1) = t(SS1)

t(CC1) = [200/s(C)]
t(EE1) = [160/s(E)]
t(SS1) = [140/s(S)]

So ...
[160/s(E)] = [140/s(S)]
[s(E)/S(S)] = (160/140) = (8/7)

s(E) : s(S)
8 : 7

By the time E completed race,
t(E1E2) = t(S1S2)

Since time taken is constant / common,
Distance ratio = Speed ratio

Given that the girls ran at constant speed throughout race,

s(E) : s(S)
8 : 7
d(E1E2) : d(S1S2)
8 : 7

8u --> 40
1u --> 5

d(S1S2) = 7u --> 7 × 5 = 35 m

60 - 35 = 25 m

========

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By: echeewh (offline)  Tuesday, August 26 2014 @ 03:15 AM CDT  
echeewh

hey <Kuro>

Kindly refer to attachment for worked solution to Q1.

Trust this helps.

Do let me know again if there's further clarification.

Cheers,
Edward


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