Q&A - PSLE Math

[jieheng]

5/9 (the mass of flour she left after she use 4/9 for pizza)


5/7 (the mass of flour she left after she use 2/7 for cake)


The mass of the packet of flour that she left is

=5/9 * 5/7 * 2

=0.79 kg

[shurley197323]

Pls help.

1) Ms Lam wants to give some sweets to her pupils. If she gives 7 sweets to each pupil, she will have 380 sweets left. If she gives 15 sweets to each pupils ,she will have 76 sweets left.
(a) How many pupils are there ?
(b) How many sweets does Miss Lam have?

(Not allow to use guess & check methods)

(2) Sue bought an equal no of oranges & pears. Oranges cost 7 for $2 and pears cost 5 for $3. She paid $33 more for pears than oranges.
(a) How much did Sophia pay?
(b) How many oranges and pears did she buy altogether?

[jieheng]

Q1


a)

The difference between the sweets = 380 - 76 = 304

Extra sweets for each pupil = 15 - 7 = 8

No. of pupils = 304 / 8 = 38 (Ans)

b)


No. of sweets that Miss Lam has = 38 * 7 + 380 = 646 (Ans)

OR

No. of sweets that Miss Lam has = 38 * 15 + 76 = 646 (Ans)

[jieheng]

Q2


One set of equal no of oranges and pears = 7 * 5 = 35

Cost of 35 oranges = 35 / 7 * 2 = $ 10

Cost of 35 pears = 35 / 5 * 3 = $ 21

The difference between one set of fruits = 21 - 10 = $ 11

Given she paid $ 33 more for pears than oranges

No. of sets of fruits = 33 / 11 = 3

a) She paid = 3 * ( 10 + 21) = $ 93 (Ans)

b) No. of oranges and pears she bought = 3 * (35 + 35) = 210 (Ans)

[shurley197323]

Thanks jieheng. Don’t mind 1 more question.

2/5 of the counters in a box were red and tge rest were blue.
After putting 48 blue counters in the box, 3/4 of the counters were blue. How many counters were in the box at first?

[jieheng]

At First

Red Blue
2u 3u

+ 48counters

New Ratio 1u 3u
Change to 2u 6u
(There is no change in the no. of Red counters)


Different in the ratio of after and before for blue counters = 6u - 3u =3u
3u----->48

1u----->16

No. of counters at first = 5 u = 5 * 16 = 80 (Ans)

[shurley197323]

jieheng:

At First

Red Blue
2u 3u

+ 48counters

New Ratio 1u 3u
Change to 2u 6u
(There is no change in the no. of Red counters)


Different in the ratio of after and before for blue counters = 6u - 3u =3u
3u----->48

1u----->16

No. of counters at first = 5 u = 5 * 16 = 80 (Ans)

Hi.sorry .My kid had not learn ratio yet. Got other solution?

[jieheng]

At First ,


Red [][]

Blue [][][]

After ,

Red [][]

Blue [][][] + 48

Red is 1/4 , Blue is 3/4

Red * 3 = Blue

[][] [][] [][] = [][][] + 48

[][][] = 48

[] = 16

At First ,

There are [][][]][] = 5 * 16 = 80 counters (Ans)





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[shurley197323]

Thanks, thnaks jieheng, hope you won’t feel frustrated to answer so many questions.

[jieheng]

shurley197323:

Thanks, thnaks jieheng, hope you won't feel frustrated to answer so many questions.

Hi ,

You are welcome.

No problem.

Regards,