Q&A - PSLE Math

[MathIzzzFun]

iamproudparents:

http://i46.tinypic.com/35hr769.jpg\">

Cross-multiply/UP (units-parts) method:

At first, John's money : Daisy's money --> 1 unit : 8 units
In the end, John's money : Daisy's money
-> 1 unit - $80 : 8 units - $985
= 3 : 1 (or 3 parts : 1 part)

Cross-multiply / Equalize parts:

1 unit - $80 = 24 units - $2955
1 unit --> $125

John's money, at first --> $ 125


cheers.

[MathIzzzFun]

iamproudparents:

http://i48.tinypic.com/2usex3d.jpg\">

by train --> 7/10 tour = 14/20 tour
by coach --> 1/4 tour = 5/20 tour

1 - 14/20 - 5/20 = 1/20

by car --> 1/20 tour

14/20 - 1/20 = 13/20

13/20 tour --> 416 km
tour --> 416 km/13 x 20 = 640 km

total distance pf the tour = 640 km

cheers.

[MathIzzzFun]

iamproudparents:

http://i48.tinypic.com/5a8w1.jpg\">

$0.90 = $0.50 + 2 x $0.20 --> 1 x 50-cent + 2 x 20-cent
Total amount left = $16.20 - $0.90 = $15.30

1 set of (3 x 50-cent coin + 1 x 20-cent coins) = $1.50 + $0.20 = $1.70
Number of sets = $ 15.30 / $ 1.70 = 9

At first,
number of 20-cent coins --> 9 + 2 = 11
number of 50-cent coins --> 9 x 3 + 1 = 28

cheers.

[MathIzzzFun]

iamproudparents:

http://i47.tinypic.com/3442yxz.jpg\">

a) 30 dots used, number of dots per side = 30/5 + 1 = 7
or (30+5)/5 = 7

b) 47 dots per side, total --> (47-1) x 5 = 230
or 47 x 5 - 5 = 230

cheers.

[MathIzzzFun]

iamproudparents:

http://i46.tinypic.com/2zyzul5.jpg\">

a)
total number = sum of squares
pattern 1 = 1² = 1
pattern 2 = 1² + 2² = 5
pattern 6 = 1² + 2² + 3² + 4² + 5² + 6² = 91

b)
total number of cubes = 27 405 / 27 = 1015
use the calculator and add the squares to 1015

pattern 14 = 1² + 2² + 3² + 4² ......+ 13² + 14² = 1015

(* shortcut : number of cubes in pattern N = N(N+1)(2N+1)/6 )

cheers.

[MathIzzzFun]

iamproudparents:

http://i47.tinypic.com/13zbs54.jpg\">

If Alice gives $46 to Naga, they will have the same amount of money. If Naga gives $17 to Alice, she will have 8 times as much as him. How much does Alice have ?

If Alice gives $46 to Naga, they will have the same amount of money
--> Alice has $46 x 2 = $92 more than Naga.

If Naga gives $17 to Alice, Alice will have 8 times as much as Naga (Alice --> 8 units, Naga --> 1 unit)
--> Alice will have $92 + $17 x 2 = $126 more than Naga
so, 7 units --> $126, 1 unit --> $18

Alice's money --> 8 x $18 - $17 = $127

cross-multiply/UP (units-parts method):

If Alice gives $46 to Naga, they will have the same amount of money:
Alice's money : Naga's money = 1u : 1u

AT FIRST, Alice's money : Naga's money = 1u + $46 : 1u - $46

If Naga gives $17 to Alice, Alice will have 8 times as much as Naga:
Alice's money : Naga's money
1u + $46 + $17 : 1u - $46-$17
= 1u + $63 : 1u - $63
= 8 : 1 (or 8 parts : 1 part)

cross-multiply /Equalize parts:
1u + $63 = 8u - $504
1u --> $81

Alice's money --> $81 + $46 = $127


cheers.

[Mum1113]

Hi, kindly help this pls, thanks!


Jack,.Meili and Raj shared some 50 cent coins.
They each had an average of 28 coins.
The total amount of money that Jack and Meili had was $7 more than
the total amount of Jack and Raj had.
If Raj’s amount was 4 times of Jack’s amount, how much more money
did Meili have than Jack?

[tianzhu]

Mum1113:

Hi, kindly help this pls, thanks!


Jack,.Meili and Raj shared some 50 cent coins.
They each had an average of 28 coins.
The total amount of money that Jack and Meili had was $7 more than
the total amount of Jack and Raj had.
If Raj's amount was 4 times of Jack's amount, how much more money
did Meili have than Jack?

Hi

Where is this question from?

Please help to confirm the numbers from your source.

Best wishes

[mummyv]

tianzhu:

Mum1113:

Hi, kindly help this pls, thanks!


Jack,.Meili and Raj shared some 50 cent coins.
They each had an average of 28 coins.
The total amount of money that Jack and Meili had was $7 more than
the total amount of Jack and Raj had.
If Raj's amount was 4 times of Jack's amount, how much more money
did Meili have than Jack?

Hi

Where is this question from?

Please help to confirm the numbers from your source.

Best wishes

This is Rosyth 2012 ca1 q14. No ans provided.

my attempt

Total money 28 x 3 x $0.50 = $42

J - u
R - u u u u
M - u u u u $7

1u = ($42 - $5)/9 = 35/9
M-J = 3u +$7 = (3 x 35/9) + $7 = $18 2/3

[mummyv]

Pls help w this St Nicks CA1 2012, thanks http://i45.tinypic.com/35a4v7p.jpg\">