
By: hehe88 (offline) Thursday, September 09 2010 @ 07:25 AM CDT (Read 2464 times)



hehe88 
Hello everyone!
I need help in some of the pri6 prelim questions below.. Any help rendered will be appreciated!
1) the ratio of the amount of money Colin has to the amount of money Daniel has is 4:7. After each of them spends $28, their ratio becomes 3:7. Find the amount of money Colin has now.
2) Michelle's house and Natasha's house are 480m apart. Both girls walked from their house to the park at the same time. Michelle caught up with Natasha after 40 mins. Given that Natasha's speed is 68m/min, find the time taken for Michelle to walk from her house to Natasha's house.
3) Mrs Lim brought some forks and spoons in the ratio of 4:3. Each spoon cost $0.50 more than each fork. If she spent $156 altogether and the amount she spent on the forks was #12 more than the amount she spent on the spoons, how many forks and spoons did she buy?
4) Tracy counted the number of 10 cent coins, 20 cent coins and 50 cent coins in her piggy bank. The number of 10 cent coins was 24 more than the number of 50 cent coins. After spending 3/5 of the 10 cent coins, 1/4 of the 20 cent coins and 18 of the 50cent coins, she had an equal number of 10cent and 20cent coins. The number of 50cent coins now formed 40% of the remaining number of coins.
a) How many 10cent coins did Tracy have at first
b) How much did she spend in all?

Newbie
Registered: 09/08/10 Posts: 1





By: rathanackumr (offline) Thursday, September 09 2010 @ 01:33 PM CDT



rathanackumr 
Before
C : D
4 : 7 Multiply both sides by 4 > 16 : 28
Change
Each of them spends $28.
After
C : D
3 : 7 Multiply both sides by 3 > 9 : 21
Note that the difference for Colin = (169) = 7 units and
the difference for Daniel = (2821) = 7 units
meaning that both difference are equal as they spend equal amount of money.
7 units = $28 , 1 unit = $4
Now, Colin has 9 units means $4x9 = $36

Junior
Registered: 07/22/10 Posts: 18





By: rathanackumr (offline) Thursday, September 09 2010 @ 02:40 PM CDT



rathanackumr 
Q 2
Michelle house Natasha house Park
<>......................................<>..............................<>
{ 480m }
Recommended method ( which will make sense to most kids)
Natasha speed = 68 m/min, Time = 40min ,
so Distance =68x40 = 2720m
Michelle's Distance covered = 2720m+480m = 3200m, Time =40min
so speed of michelle = 3200/40 = 80m/min
At 80m/min michelle will take 480/80 = 6 mins to reach Natasha house

Junior
Registered: 07/22/10 Posts: 18





By: rathanackumr (offline) Thursday, September 09 2010 @ 02:45 PM CDT



rathanackumr 
Q2 Another method much faster , This involves adding the speed it takes to walk the extra 480m in 40 mins to Natasha's speed in the same time
480m in 40 mins = 480/40 = 12m/min
68m/min+ 12m/min= 80m/min
so 480/80 = 6 mins

Junior
Registered: 07/22/10 Posts: 18





By: mumof2boys (offline) Friday, September 10 2010 @ 11:06 PM CDT



mumof2boys 
CHK OUT THE ATTACHMENT FOR SOLUTION TO FORK AND SPOON PROBLEM
F:S = 4:3
Total spent=$156
amt spent on forks = 12 + (15612)/2= 84
amt spent on spoons = 72

! F !F ! F ! F !S ! S ! S !

$84 divided into 4 parts = $21 (amt spent on each block of forks)
$72 divided into 3 parts + $24 (amt spent on each block of spoons)
since each spoon costs 0.5 more than a fork, $24  $21 = $3, $3 is spent more on the whole no. of spoons.
$3 divided by 0.5 = 6
so each block consists of 6 units.
so no. of forks = 4X6 = 24 and no. of spoons = 3X6=18

Newbie
Registered: 08/22/09 Posts: 6





By: naggyaunty333 (offline) Monday, September 20 2010 @ 04:34 AM CDT



naggyaunty333 
For the last question:
Simply use models(or ratio).
Firstly, 2/5 of the 10cents is equal to 3/4 of the 20cents, so the ratio is 10cent:20cent = 15:8
Then, 6+6 units is 60%(because they spent some of the coins) and 1 unit is 5%.
Next, since 50cents is 40% there are 8 units worth of 50cents left after spending.
Time to bring in the numbers. Since there are now more 50cent units than 10cent units, you can figure out the number of coins each unit represents simply by doing this:
24+18 = 42 and 42 is 7 units.
And I think the rest is crystal clear by now.

Newbie
Registered: 04/25/10 Posts: 1



