Q&A - PSLE Math

[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.

[lulu2014]

1) Siti, Weiling and Radha baked the same number of cookies each. If Siti gave 44 cookies to Weiling and 80 cookies to Radha, the number of cookies Weiling and Radha have will be 4 times as many as Siti's cookies. How many cookies did each of them bake?

[Ender]

1) Siti, Weiling and Radha baked the same number of cookies each. If Siti gave 44 cookies to Weiling and 80 cookies to Radha, the number of cookies Weiling and Radha have will be 4 times as many as Siti's cookies. How many cookies did each of them bake?

Let the number of cookies they each baked at first be u

Scenario
Siti gave away a total of 124 cookies
Siti is left u - 124

Weiling gain 44,
Weiling will have u + 44
Radha will have u + 80
Total both of them will have 2u + 124

4 X (u-124) = 2u + 124
4u - 496 = 2u + 124
2u = 620
u = 310

[Fly2high]

Thanks very much Ender !!

[angel]

Fruit seller has some apples and pears.
If he sells twice as many pears as the apples, he would have 207 apples left when all pears are sold.
If he sells twice as many apples as the pears, he would have 72 apples left when all pears are sold.
a) How many pears does the fruits seller have?
b) Mrs Tan buys all pears from the seller. The rice is 80cts. For every 3 pears she buys, she gets one more at half the price.
How much does Mrs Tan pay for all pears?

[angel]

A repeated pattern is formed using 4 letters A, B, C and D.
The first 16 letters are as follow.
A B C D D C B A A B C D D C B A
How many 'D' are there in the first 125 letters?

[Ender]

Fruit seller has some apples and pears.
If he sells twice as many pears as the apples, he would have 207 apples left when all pears are sold.
If he sells twice as many apples as the pears, he would have 72 apples left when all pears are sold.
a) How many pears does the fruits seller have?
b) Mrs Tan buys all pears from the seller. The rice is 80cts. For every 3 pears she buys, she gets one more at half the price.
How much does Mrs Tan pay for all pears?

Scenario 1
If she sells 2u of pears and she sells 1u of Apple

The number of Apples = 1u + 207
The number of Pears = 2u

Scenario 2
If she sells 2p apples and 1p of pears
The number of Apples = 2p + 72
The number of Pears = 1p

The number of pear we know 2u = 1p. We can subsitute in one of the Apple Equation. I take the 2nd Apples equation

Apples = 2p + 72 = 4u + 72

4u + 72 = 1u + 207 , they are both equations for the number of Apples.
3u = 135
u = 45

a) Pears = 2u = 2(45) = 90##

b)Every fourth pear is half price. So 1st we find how many of these fourth(1/2 price) pear are among the 90 pears.

Number of 1/2 price pear 90/4 roughly round down to 22 pears.

The number of pears are full price = 90-22 = 68

Cost of 1/2 price pears = 22 X 0.4 = $8.80
Cost of full price pear = 68 X 0.8 = $54.4

Total spending = 8.8 +54.4 = $63.20 ###

[Fly2high]

Hi , pls help on the below .


The ratio of Alvin's savings to Bernard's savings was 3:11 after
Alvin gave 1/10 of his savings to Bernard . Both later spent the
Same amount of money at a book fair . In the end, the ratio of Alvin's
Savings to Bernard's savings became 1:9 and Bernard had $264
More than Alvin .

A) what was the ratio of Alvin's savings to
Bernard's savings at first ?
B) how much savings did Alvin had at first ?

Thanks & Regards
Fly2High

[Ender]

A repeated pattern is formed using 4 letters A, B, C and D.
The first 16 letters are as follow.
A B C D D C B A A B C D D C B A
How many 'D' are there in the first 125 letters?

The pattern repeats after 8 characters. i.e
ABCDDCBA

125/8 = 15 + 5/8

This means there are 15 sets of ABCDDCBA Plus the first 5 character of the set, i.e. ABCDD.

Each set there are two Ds. While the first 5 characters ABCDD includes another two Ds.

Total Ds = 2X 15 + 2 = 32 ##

[Ender]

Hi , pls help on the below .


The ratio of Alvin's savings to Bernard's savings was 3:11 after
Alvin gave 1/10 of his savings to Bernard . Both later spent the
Same amount of money at a book fair . In the end, the ratio of Alvin's
Savings to Bernard's savings became 1:9 and Bernard had $264
More than Alvin .

A) what was the ratio of Alvin's savings to
Bernard's savings at first ?
B) how much savings did Alvin had at first ?

Thanks & Regards
Fly2High

In the end, The saving A :B => 1 : 9
And B has $264 more.

B - A = 264
9u - 1u = 264
8u = 264
u = 33

So in the end
Alvin had $33
Bernard had 9u = $297

Before Spending
Let Spending be p
Alvin has $33 + p = 3n
Bernard has $297 + p = 11n

297 + p - 33 - p = 11n - 3n
264 = 8n
n = 33

So before Spending
Alvin had 3n = $99
Bernard had 11n = $363

a) at first, before ALvin gave 1/10 of his saving to Bernard.

Alvin's
9/10 => $99
10/10 => $110
He gave $11 to Bernard

Bernards = 363 -11 = $352 at first.

Ratio at first =110 : 352 => 5 : 16 ###

b) at first Alvin has $110 ###