Q&A - PSLE Math

[2DMommy]

Need help again,


1) Danny and Richard earned a total of $3850. Richard earned $1850 more than Danny. Danny earned $5 more than Richard each day and Richard worked 3 times as many days as Danny. How much did Richard earn each day ?

2) Tom bought some chocolates and gave half of them to John. John bought some swees and gave half of them to Tom. Tom ate 12 sweets and John ate 18 chocolates. After that, the number of sweets and chocolates Tom had were in the ratio 1:7 and the number of swees and chocolates John had were in the ratio 1:4. How many sweets did John buy ?

Thank you.

[dicoyote]

hi, am not able to identify the model to use for this question, thus seeking help, thanks in advanced


A shopkeeper had some blue and red pens in his book shop. There were twice as many red pens as blue pens. The shopkeeper sold the pens in bundles of 2 red pens and 3 blue pens. After selling all the blue pens, he still had 120 red pens left. How many pens did he have in his bookshop at first?

[the shadowed snake]

Michaelia0816:

(2)Mrs Hoon made some cookies to sell. 3/4 of them were chocolate cookies and the rest were almond cookies. After selling 210 almond cookies and 5/6 of the chocolate cookies, she had 1/5 of the cookies left. How many cookies did Mrs Hoon sell?

hi is the ans 252 or 960? :lol:

[Michaelia0816]

I think it is 960, due to my calculation

[Michaelia0816]

Thanks, the shadow snake, for your time to help to solve!

[charsen]

dicoyote:

hi, am not able to identify the model to use for this question, thus seeking help, thanks in advanced


A shopkeeper had some blue and red pens in his book shop. There were twice as many red pens as blue pens. The shopkeeper sold the pens in bundles of 2 red pens and 3 blue pens. After selling all the blue pens, he still had 120 red pens left. How many pens did he have in his bookshop at first?

Hi,
This Question is a two ratio problem and could be solved by cross multipication.
First,You subtract 120 from 2U.The 2U refers to the red pen at first.I am doing this so that the ratio of the pens at first is equal to the Selling ratio , which is 2:3.
If you cross multiply now,
(2U-120)x3=6U-360
6U-360=(2x1)u
4U=360
1U=360/4=90
no.of pens at first-3U-90x3=270(ans)
cheers

[Michaelia0816]

Am I right?, Tianzhu?

[MathIzzzFun]

dicoyote:

hi, am not able to identify the model to use for this question, thus seeking help, thanks in advanced


A shopkeeper had some blue and red pens in his book shop. There were twice as many red pens as blue pens. The shopkeeper sold the pens in bundles of 2 red pens and 3 blue pens. After selling all the blue pens, he still had 120 red pens left. How many pens did he have in his bookshop at first?

Hi

note that the number of blue pens sold = total number of blue pens

At first,
Red pens : Blue pens = 2 : 1 --> 6u : 3u -- total number of pens --> 9u
Sold,
Red pens : Blue pens --> 2u : 3u
Number of red pens left --> 4u = 120, 1u --> 30
Total number of red & blue pens at first = 9 x 30 = 270.

cheers.

[MathIzzzFun]

2632parent:

Need help on this question, just cannot get the answer?


1) Mr Wu and Mr Zheng travelled along the same expressway to Town M. Mr Wu left his flat at 6.20am and travelled at 90km/h. 40 minutes later, Mr Zheng left for Town M and drove at an average speed of 105 km/h. At what time did they meet on the way?

Thank you

Hi

Using speed/time ratio,

Mr Wu's speed : Mr Zheng's speed = 90 : 105 = 6u : 7u
When they meet on the way, time taken by Mr Wu : Mr Zheng --> 7u : 6u
1u --> 40 min
7 x 40 = 280 min = 4h 40 min
6.20am + 4h 40min --> 11am
They met at 11am
------------------------------
alternatively, you can also use the difference in speed to work out the time they will meet.

When Mr Zheng left for Town M, Mr Wu would have travelled 40 min x 90km/h = 60 km

105 km/h - 90 km/h = 15 km/h --> Mr Zheng would catch up 15 km every hour

60 /15 = 4h --> Mr Zheng caught up with Mr Wu after 4h
6.20am + 40 min + 4h --> 11 am

They met at 11 am

cheers.

[elkniwt]

Hello,


Need help in this qn from Henry Park 2011 Prelim :

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Thanks!!