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Saturday, April 29 2017 @ 11:57 PM CDT
 Forum Index >  Test Paper Related >  Primary 5 Matters
 4 operations of decimals
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By: smallducky (offline)  Thursday, August 09 2012 @ 09:50 AM CDT (Read 861 times)  
smallducky

Hello , I need help for these two questions please help me with working solution.

4) Mr Ho and Mr Sim had the same amount of money at first. Mr Ho spent 20% of his money on some books. Then mr sim was given another $500 and mr ho spent another $600 and the ratio of the amount of money that mr ho had to the amount of money that mr sim had become 3 : 5.
(a) Find the amount of money mr sim had at first.
(b) what fraction of his amount of money did mr ho have in the end?


(5) 0.4 of the balls in a box were black while the rest were red. When 0.25 of the black balls and 0.75 of the red balls were taken out of the box, there were 9 balls left in the box. How many red balls were there in the box at first?


Thanks in advance
Smallducky

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By: jo sarah (offline)  Saturday, August 11 2012 @ 10:41 AM CDT  
jo sarah

(4) tabulate:
........................Ho......................Sim
at first:.............1u........................1u
change:....-(0.2u+600)............+(500)
in end:........0.8u - 600............1u + 500
in ratio:............3p.........................5p

(a) So, 0.8u - 600 = 3p
x5: 4u - 3000 = 15p
and, 1u + 500 = 5p
x3: 3u + 1500 = 15p
thus, 4u - 3000 = 3u + 1500
therefore, 1u = 4500
Mr Sim had $4500 at first.

(b) 0.8u - 600 = 0.8 x 4500 - 600 = 3000
So that Mr Ho had 3000/4500 = 2/3 of his money in the end.

(5) .....................black............red
at first:..................4u...............6u
change:...............-1u.............-4.5u
in end:..................3u..............1.5u

total in end: 4.5u = 9 balls
so, 1u = 2
and there were 10u = 20 balls in the box at first.

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By: smallducky (offline)  Saturday, August 11 2012 @ 11:01 PM CDT  
smallducky

Thanks for help, jo sarah.

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