Q&A - PSLE Math

[oovi-yah]

pls help me on these 3 questions


1.Ali,bala ,clyde and dingyi shared a box of pens.ali received 20% of the total number of pens which bala ,clyde and dingyireceived altogether .bala received 50% of the total number of pens which ali,clyde and dingyi received altogether.clyde received 80% of the total number of pens which ali,bala and dingyi received altogether.dingyi received 6 pens.how many pens were in the box at first?

2.jolene and penny had a sun of money.jolene gave penny 0.4 of her money .penny then gave jolene 1/2 of her money.in the end jolene had three times the amount of money that penny had.if jolene gave penny $125 more than what penny gave jolene,how much money did jolene have at first?

3.Mrs.raju bought 20 bottles of milk and 5 boxes of cornflakes from supermarket.if she had bought these items at 20% discount,the amount of money she saved could buy another 3 more boxes of cornflakes at the usual price.the usual price of a bottle of milk was 2.15.what was the usual price of a box of cornflakes?

[starlight1968sg]

oovi-yah:

pls help me on these 3 questions


1.Ali,bala ,clyde and dingyi shared a box of pens.ali received 20% of the total number of pens which bala ,clyde and dingyireceived altogether .bala received 50% of the total number of pens which ali,clyde and dingyi received altogether.clyde received 80% of the total number of pens which ali,bala and dingyi received altogether.dingyi received 6 pens.how many pens were in the box at first?

2.jolene and penny had a sun of money.jolene gave penny 0.4 of her money .penny then gave jolene 1/2 of her money.in the end jolene had three times the amount of money that penny had.if jolene gave penny $125 more than what penny gave jolene,how much money did jolene have at first?

3.Mrs.raju bought 20 bottles of milk and 5 boxes of cornflakes from supermarket.if she had bought these items at 20% discount,the amount of money she saved could buy another 3 more boxes of cornflakes at the usual price.the usual price of a bottle of milk was 2.15.what was the usual price of a box of cornflakes?

1) A: B+C+D = 20:100 = 1:5
B: A+C+D = 50:100 = 1:2
A+B+D = 80:100 = 4:5

Since the total number of pens involved is the same for the above 3 cases, find the LCM of 6,3,9 which is 18.

Thus the ratios become
A:B+C+D = 3:15
B:A+C+D = 6:12
C:A+B+D = 8:10

A:B:C: D = 3:6:8: ONE to make up the total of 18.
Thus D has 1 part which is 6 pens.
Total parts = 18 and thus 18*6 = 108 pens.

2) Draw models:
J has 10 units, Penny has 1 part.
J gave 4 u to Penny.
Thus Penny has 1 p + 4u.
Then Penny gave J half of what she has ie 1/2 P + 2u.
After that J has thrice as what Penny has.
So, 6u = 2 (1/2P +2u) = P+4u
P=2u.

J gave 4u to Penny.
Penny gave 1/2P + 2u = 3u to J.
Their difference is 1u which corresponds to $125.

J has 10u = $1250.

[iFruit]

oovi-yah:

pls help me on these 3 questions


3.Mrs.raju bought 20 bottles of milk and 5 boxes of cornflakes from supermarket.if she had bought these items at 20% discount,the amount of money she saved could buy another 3 more boxes of cornflakes at the usual price.the usual price of a bottle of milk was 2.15.what was the usual price of a box of cornflakes?

20% of 20 bottles of milk = 1/5 x 20 x2.15 = 8.6

Let price of a box of cornflakes = u

20% of 5 boxes of cornflakes = 1/5 x 5 x u = u

8.6 +u = 3u ----> 2u = 8.6 ---> u = 4.3

Usual price of a box of cornflakes = $4.30

[tianzhu]

Hi


Hope this helps.

Best wishes

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[Dharma]

iFruit:

oovi-yah:

pls help me on these 3 questions


3.Mrs.raju bought 20 bottles of milk and 5 boxes of cornflakes from supermarket.if she had bought these items at 20% discount,the amount of money she saved could buy another 3 more boxes of cornflakes at the usual price.the usual price of a bottle of milk was 2.15.what was the usual price of a box of cornflakes?

20% of 20 bottles of milk = 1/5 x 20 x2.15 = 8.6

Let price of a box of cornflakes = u

20% of 5 boxes of cornflakes = 1/5 x 5 x u = u

8.6 +u = 3u ----> 2u = 8.6 ---> u = 4.3

Usual price of a box of cornflakes = $4.30

4 bottles of Milk + 1 box of cornflakes = 3 boxes of cornflakes
2 boxes of cornflakes = 4 bottles of milk
1 box of cornflakes = 2 bottles of milk = 2 x $2.15 = $4.30

[starlight1968sg]

Hello,

I need help on:
In a school, the ratio of the number of pupils wearing glasses to the number of pupils not wearing glasses is 11:5.
2/3 of the boys and 7/10 of the girls wear glasses.
What is the ratio of the number of boys to the number of girls?
Many thanks.

[Dharma]

starlight1968sg:

Hello,

I need help on:
In a school, the ratio of the number of pupils wearing glasses to the number of pupils not wearing glasses is 11:5.
2/3 of the boys and 7/10 of the girls wear glasses.
What is the ratio of the number of boys to the number of girls?
Many thanks.

Wear glasses : No glasses = 11 : 5

(2u + 7p ) : (1u + 3p ) = 11: 5
10u + 35p = 11u + 33p
1u = 2p

No. of boys = 3u = 6p
No. of girls = 10p

Boys : Girls = 6 : 10 = 3 : 5

[starlight1968sg]

Dharma:

starlight1968sg:

Hello,

I need help on:
In a school, the ratio of the number of pupils wearing glasses to the number of pupils not wearing glasses is 11:5.
2/3 of the boys and 7/10 of the girls wear glasses.
What is the ratio of the number of boys to the number of girls?
Many thanks.

Wear glasses : No glasses = 11 : 5

(2u + 7p ) : (1u + 3p ) = 11: 5
10u + 35p = 11u + 33p
1u = 2p

No. of boys = 3u = 6p
No. of girls = 10p

Boys : Girls = 6 : 10 = 3 : 5

Thanks so much. I have been struggling with this prob, thinking I need to find the number of boys and girls...

[SLeng]

Hi Muffins,

In your answer for Mumbest’s question, what is LCM ?

Thanks

[starlight1968sg]

SLeng:

Hi Muffins,

In your answer for Mumbest's question, what is LCM ?

Thanks

LCM = lowest common multiple.