Q&A - PSLE Math

[Ender]

Can anyone help me with these questions. Thank you.
http://imgur.com/nYsBS2D

Time taken for Lee to travel 315km = 315/90 = 3.5hr

But Wong has a 30min head start, so his traveeling time is 4hr instead.
The distance Wong covers in 4hrs = 60X4 = 240km

A) since 240k is 2/3 of journey,
3/3 of the journey = (240/2) X 3 = 360km ###

B) For 360 km,time take for mr wong is = 360/60 = 6hrs
He started at 10am, 6 hours later is 4pm ####

C) Base on Lee's start time (10:30am), which is 30min later. Wong would have closed the distance between them,
Distance WOng travelled in 30min = 60 X0.5 = 30km

Distance between Wong and Lee= 360-30 = 330km

Time take to meet, = 330/(90+60) = 2.2 hrs or 2hr and 12 min. (note, opposing direction we use sum of speed. If they are travelling the same direction we use the difference in speed)

From 10:30am, another 2h and 12 mins later, the time will be = 12:42pm ### That's whn they meet.

[Ender]

Can anyone help me with these questions. Thank you.
http://imgur.com/mO4eVcm

If Tom had 5u. 4/5 would be 4u
4u is half of Ali's, that mean Ali has 8u

Therefore,
Tom has 5u
Ali has 8u

If Ali gave 110 stamps,
Leftover for ALi = 8u - 110

If Tom ought 80 stamps,
Tom would have = 5u + 80

Ali is 3/4 of TOm,
8u - 110 = 3/4 (5u +80)
8u - 110 = 3.75u + 60
4.25u = 170
u = 40

Total number of stamp at first = 8u + 5u = 13u = 520 stamps ###

[Ender]

Hi , pls help on the below question.

Mrs Wendy had some banana muffins , chocolate muffins and vanilla muffins.
She had 260 more vanilla muffins than chocolate muffins.
She sold 60% of the banana muffins , 2/3 of the chocolate muffins and 3 times
As many vanilla muffins as chocolate muffins. Thereafter, she took stock and
Found that she had 25% of her vanilla muffins left . The total number of the 3types
Of muffins became 212.

Find the total number of muffins she had at first ?

Thanks and regards
Fly2High

Let Banana be 100p
Let choc be 30u,
Vanilla will be 30u + 260

She sold 2/3 of choc which is 20u. And for vanilla sold 3 times as many. That means she sold 60u of vanilla.

Choc left = 10u
Vanilla left = 30u+260 - 60u = 260-30u

Vanilla left is 25% of orignal. Or original is 4 times as many as left over
30u + 260 = 4 (260-30u)
30u + 260 = 1040 - 120u
150u = 780
u = 5.2

Leftover Choc = 10u = 52
Lefotver vanilla = 260 - 30u = 104

Leftover muffins, 212 = 52 + 104 + Leftover banana
Left over banana = 212-156 = 56
Since 40 % => 56
100% => 56/0.4 = 140 bananas originally

Original Choc = 30u = 156
Oriignal Vanilla = 30u+260 = 416

Total muffins at first = 416 + 156 +140 = 712 ###

[snowball14]

Selina bought a concert ticket at 10% discount and then sold it away to her friend at $20 more than original price.
If she earned $50, what is the original price of the ticket?

[Ender]

Selina bought a concert ticket at 10% discount and then sold it away to her friend at $20 more than original price.
If she earned $50, what is the original price of the ticket?

We let Original ticket be 100u
So she bouth at 90u (10% discount) => Cost Price

Ticket sold at 100u + 20 => Selling Price

Profit of $50
Selling price - cost price = $50
100u + 20 - 90u = $50
10u = 30
u = 3

Orignal price of ticket is 100u = $300 ###

[Fly2high]

Thanks very much Ender !!

[Fly2high]

Hi Ender ,

Pls explain why we need to assume banana as 100p and chocolates as 30u ..


Regards
Fly2High

[questionable_i]

Srry again, I need help again.

[Ender]

Srry again, I need help again.

6. Now, May is P + 5
Now,brother is P + 5 - 3 = P + 2
Total = P + 5 + P + 2 = 2P +7 ##
_________________________________________________________
22. If Ali has 100u. His sister recieved which is 30u. She spent 60% of 30u = 18u
So % of Ali's saving that she spent = (18/100) X 100 = 18%##
_________________________________________________________
30. Right angle isosceles triangle can form a square with four of them.
As in the picture, you can form a 20 cm X 20 cm square with four of them. And one triangle is 1/4 of the square.
20 X 20 = 400 cm2
Area of triangle is 1/4 X 400 = 100cm2

[Ender]

Hi Ender ,

Pls explain why we need to assume banana as 100p and chocolates as 30u ..


Regards
Fly2High

It depends on what is mathematical operations is going to happen to them. Just like modelling, how many boxes to choose? It depends on the mathematical operations.

e.g. for banana muffin, She will sell 60%, and left with 40%. A nice number working with percentage would be 100u . 60% of 100u will be 60u. Fast and easy.

For choc, the mathematical operation will be 2/3 of it sold off, with 1/3 left. I have to select a number of 'u' has to be able to be divided or split into 3 parts. I could select 3u, or 9u and it would work. 30u was my choice.