Sign Up!
Login
Welcome to Test-paper.info
Tuesday, August 22 2017 @ 02:08 AM CDT
 Forum Index >  Test Paper Related >  Primary 5 Matters
 P5 Mathematics.
   |  Printable Version
By: verachen (offline)  Saturday, May 12 2012 @ 10:30 AM CDT (Read 1655 times)  
verachen

Four boys, Alex, Bryan, Calvin and Derrick, each have some stamps.The number of stamps Alex has is 1/2 of the total of Bryan, Calvin and Derrick have. The number of stamps Bryan has is 1/3 of the total of Alex, Calvin and Derrick have. The number of stamps Calvin has is 1/4 of the total of Alex, Bryan and Derrick have. If Derrick has 78 stamps, find the total number of stamps Alex and Bryan have altogether.

Please help asap as the question may come out in my SA1. ^.^ Thanks!

Forum Junior
Junior

Registered: 05/07/10
Posts: 15

Profile Email    
   
By: MathIzzzFun (offline)  Saturday, May 12 2012 @ 09:42 PM CDT  
MathIzzzFun

Quote by: verachen

Four boys, Alex, Bryan, Calvin and Derrick, each have some stamps.The number of stamps Alex has is 1/2 of the total of Bryan, Calvin and Derrick have. The number of stamps Bryan has is 1/3 of the total of Alex, Calvin and Derrick have. The number of stamps Calvin has is 1/4 of the total of Alex, Bryan and Derrick have. If Derrick has 78 stamps, find the total number of stamps Alex and Bryan have altogether.

Please help asap as the question may come out in my SA1. ^.^ Thanks!



Hi

Total number of stamps remain unchanged.

A : B+C+D --> 1 : 2
A: A+B+C+D --> 1:3

B: A+C+D --> 1:3
B:A+B+C+D--> 1:4

C:A+B+D --> 1:4
C:A+B+C+D--> 1:5

A+B+C+D : A:B:CBig Grin --> 60: 20: 15 : 12 : (60-20-15-12)
A+B+C+D : A:B:CBig Grin --> 60units : 20units : 15units : 12units : 13units
13 units --> 78, 1 unit --> 6

A+B --> 35 x 6 = 210

cheers.

Forum Chatty
Chatty

Registered: 04/02/10
Posts: 36

Profile Email    
   
By: verachen (offline)  Saturday, May 12 2012 @ 11:00 PM CDT  
verachen

Sorry but I don't really get why is it A : B : C : D --> 60 : 20 : 15 : 12?


Thanks.

Forum Junior
Junior

Registered: 05/07/10
Posts: 15

Profile Email    
   
By: echeewh (offline)  Sunday, May 13 2012 @ 12:17 AM CDT  
echeewh

Hey Vera,

Apply "Unchanged Total" concept (since all 3 comparisons are involving same A, B, C and D, and total number of stamps is the same in all 3 comparisons)

A : B+C+D | Total
1 : 2 3 --- (1)

B : A+C+D
1 : 3 4 --- (2)

C : A+B+D
1 : 4 5 --- (3)

Based on the concept, find lowest common multiple of 3, 4, 5. This gives 60. Hence, we have ...

(1)x 20:
20 : 40 60

(2)x 15:
15 : 45 60

(3)x 12:
12 : 48 60

Hence, A=20u, B=15u, C=12u, D=60u - 20u - 15u - 12u = 13u

Given D = 78 stamps, we have D = 13u --> 78
Therefore, 1u --> 78 / 13 = 6

A + B = 20u + 15u = 35u --> 35 x 6 = 210

===================================

Trust the above is now clear to you.

Cheers,
Edward

Forum Active Member
Active Member

Registered: 04/21/11
Posts: 625

Profile Email    
   
By: verachen (offline)  Sunday, May 13 2012 @ 09:06 AM CDT  
verachen

Thank you for your help, both of you. I have understood how to do the question now. Thank you very much! ^.^

Forum Junior
Junior

Registered: 05/07/10
Posts: 15

Profile Email    
   


 All times are CDT. The time is now 02:08 am.
Normal Topic Normal Topic
Locked Topic Locked Topic
Sticky Topic Sticky Topic
New Post New Post
Sticky Topic w/ New Post Sticky Topic w/ New Post
Locked Topic w/ New Post Locked Topic w/ New Post
View Anonymous Posts 
Able to Post 
HTML Allowed 
Censored Content