Q&A - PSLE Math

[MathIzzzFun]

wahwah:

Hi,

Need some urgent help with the following math questions.

The bookshelves in a library were arranged in rows of 8 shelves each.
The library bought another 4 shelves and rearranged the shelves into rows of 6 shelves each. After the rearrangement, the librarian found that he had 10 additional rows of shelves. How many shelves were there in the library in the end?

Many thanks in advance.

10 additional rows of shelves --> 10 x 6 = 60 shelves
Total number of shelves removed from original number of rows (2 were removed from each row) = 60 - 4 = 56

At first, number of rows of shelves = 56/2 = 28

In the end, total number of shelves = 28 x 8 + 4 = 228

cheers.

[MathIzzzFun]

iamproudparents:

http://i45.tinypic.com/f0w76o.jpg\">

James and Bond had $728 altogether. When James spent 1/4 of his money and Bond spend 2/3 of his, they found out that each had an equal amount of money left. How much did James have at first ?

Equal fraction/numerator method

http://www.tinyurl.com/mathizzzfun-equalfractions

Amount left :
3/4 James' money = 1/3 Bond's money
3/4 James' money = 3/9 Bond's money

James' money --> 4 units
Bond's money --> 9 units
Total --> 13 units --- $728
1 unit --> $56

Jame's money --> 4 x $56 = $224

cheers.

[wahwah]

MathIzzzFun,

Thanks so much!

[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?