Q&A - PSLE Math

[Denise]

ack bought some pens and erasers for a total of $100.10.

He spent $9.10 more on the pens than the erasers.
Each pen costs $3.70 more than each eraser.
Jack bought 6 times more ereasers than pens. How much does each pen cost?
How many pens and how erasers did he buy then?

[Dharma]

fxchow:

Hi,


Can someone help to solve this problem. TIA

Allen, Raymond and Tom ran at a speed of 5km/h, 6km/h and 7km/h respectively.
They ran along the same route and started at 6.00 am, 6.30 am and 7.00 am respectively.
When Raymond passed Allen, he gave Allen a message to pass to Tom.
What time will Tom receive the message?

for

Hi,

At 7am, Allen already travelled (5x1)km. Need to calculate time for Tom catch up this dist.

Time for Tom to catch up = 5km/ (Speed of Tom - Speed of Allen)
= 5/(7-5) = 2.5hrs.

Tom will pass Allen at 9.30am ...is the time Allen passes the message to him

[Dharma]

Denise:

ack bought some pens and erasers for a total of $100.10.

He spent $9.10 more on the pens than the erasers.
Each pen costs $3.70 more than each eraser.
Jack bought 6 times more ereasers than pens. How much does each pen cost?
How many pens and how erasers did he buy then?

Hi,

Qty:
Pens : 1 unit
Erasers : 7 units

Cost:
Pens : 1 part +$3.70
Eraser : 1 part

Value :
Pens : (1 unit)x(1 part +$3.70)
Erasers : (7 units)x(1 part)

(8 units)(1 part) +(1unit)($3.70) = $100.10
(1 unit)($3.70) - (6 units)(1 part) = $9.10

(14 units)(1 part) = $ 91
(1 unit)(1 part) = $6.50
(8 units)(1 part) = $52

(1 unit)($3.70) = $100.10 - $52 = $48.10
1 unit = 13

No. of pens : 13
No. of erasers : 13 x 7 = 91

[Denise]

Ok. I get it. Thank you very much

[fxchow]

Dharma:

fxchow:

Hi,


Can someone help to solve this problem. TIA

Allen, Raymond and Tom ran at a speed of 5km/h, 6km/h and 7km/h respectively.
They ran along the same route and started at 6.00 am, 6.30 am and 7.00 am respectively.
When Raymond passed Allen, he gave Allen a message to pass to Tom.
What time will Tom receive the message?

for

Hi,

At 7am, Allen already travelled (5x1)km. Need to calculate time for Tom catch up this dist.

Time for Tom to catch up = 5km/ (Speed of Tom - Speed of Allen)
= 5/(7-5) = 2.5hrs.

Tom will pass Allen at 9.30am ...is the time Allen passes the message to him

Hi Dharma,

I got it. Thanks so much!

[tianzhu]

Other than Guess and Check, what are the other alternatives to solve this problem?


Annie wrote her mother’s age followed by her own age to form a 4-digit number.She used the difference between their ages to subtract from the 4-digit number. Then Annie obtained the number 4489.What was Annie’s age ? (RGPS P6 Prelim 2008 Q47)

[Drdj]

Hi there,


Please help me with the following :

NanHua Prelim 2008

Qn 24
15 cats can catch 15 rats in 15 minutes. How long does it take 60 cats to cath 60 rats? [Ans = 15 mins - how do you know which qty to stay constant/change]

Qn 44
Amy, Beth and Carrie have some money. If Amy gives $3.50 to Beth, the two girls will have an equal amt of money. If Beth gives $3.50 to Amy, Amy will have thrice as much money as Beth. Carrie's share is the sum of the other two girls. How much money do they have altogether? [Answer = $56]

Misc
David paints once every 2 days. Larry paints once every 3 days.
If the 2 men met on 28th May, what is the earliest date David has to start work? [Answer = 24th May]

Thanks in advance

[tianzhu]

Hi Drdj


You don't have to click on quote each time you want to post new questions.Use it when you want to refer to it.

For new post without referencing, just click on post reply.

[Dharma]

Drdj:

Hi there,


Please help me with the following :

NanHua Prelim 2008

Qn 24
15 cats can catch 15 rats in 15 minutes. How long does it take 60 cats to cath 60 rats? [Ans = 15 mins - how do you know which qty to stay constant/change]

Thanks in advance

15 cats - 15 rats - 15 mins
1 cat - 15 rats - 225 mins
1 cat - 60 rats - 900 mins
60 cats - 60 rats - 900/60 = 15 mins
(Only change 1 independent variable at a time)

[Dharma]

Hi Drdj,


If Amy gives $3.50 to Beth

At last
Amy : 1 unit
Beth : 1 unit
Carrie : 1 part

At first
Amy : 1 unit +$3.50
Beth : 1 unit - $3.50
Carrie : 1 part

If Beth gives $3.50 to Amy

At last[/u]
Amy : 1 unit +$7
Beth : 1 unit - $7
Carrie : 1 part

1 unit + $7 = 3 units - $21
2 units = $28
1 unit = $14

1 part = 2 units = $28

Amt of money 3 of them have = 2 units + 1 part = $28 x 2 = $56