Tutor MathsGuru: Ask me for your burning Maths questions!

[blessedami]

CJM:

hi all,


need your expertise on this...

Susan wants to buy 7 dolls which are selling at the same price. However, she needs another $11.40 in order to buy them.
She then decides to buy 3 dolls instead and and $20.20 left after that. What is the cost of each doll ?

cheers..

My DS got this answer:

7-3=4
$20.20+$11.40=$31.60
$31.60/4= $7.90

Mathsguru/Dharma- please correct him if he is wrong

[blessedami]

firebird:

Dear Maths Guru


Good afternoon.

Please help me on the following P6 maths:

An equal number of girls and boys went to a party. The ratio of the number of girls who wore spectacles to the number of boys who wore spectacles was 11 : 3. The ratio of the number of boys who did not wear spectacles was 3 : 5.
a) Find the ratio of the number of boys who wore spectacles to the number of boys who did not wear spectacles.

b) There were 7 times as many girls as boys who left the party. The ratio of the number of girls to the number of boys who remained at the party became 35 : 38. If there were 560 girls remaining at the party, how many girls left the party?

Thank you
Firebird

Hi Firebird,

My DS thinks there is a typo error in this part of the question. Could you make it clearer?

With the figures given, this is the answer that he has for Part b)

Since there is an equal number of girls and boys in the beginning, the difference at the end would be
7 units-1unit= 6 units

To make the difference 6 units,
35:38 = 70:76

So, at first the ratio is,
77:77

Number of girls who left = 7 units

70units = 560
7 units = 56

Cheers,

[singmathstutor]

blessedami:

CJM:

hi all,


need your expertise on this...

Susan wants to buy 7 dolls which are selling at the same price. However, she needs another $11.40 in order to buy them.
She then decides to buy 3 dolls instead and and $20.20 left after that. What is the cost of each doll ?

cheers..

My DS got this answer:

7-3=4
$20.20+$11.40=$31.60
$31.60/4= $7.90

Mathsguru/Dharma- please correct him if he is wrong

Your son is spot on.

[maths6a]

In the figure, KE = EL, AE = ED and BC is 3 times KB. Area of rect ABCD is 94 cm2 and the area of triangle KGB is 6 cm2.

Find the area of triangle KEL.
Can anybody tell me how to draw the diagram here?
This qn can be found on the last page of My pals are here workbook 5A.
Thanks

[CJM]

blessedami:

CJM:

hi all,


need your expertise on this...

Susan wants to buy 7 dolls which are selling at the same price. However, she needs another $11.40 in order to buy them.
She then decides to buy 3 dolls instead and and $20.20 left after that. What is the cost of each doll ?

cheers..

My DS got this answer:

7-3=4
$20.20+$11.40=$31.60
$31.60/4= $7.90

Mathsguru/Dharma- please correct him if he is wrong

thank you for the answer !!
ur ds is so smart ... how old is he?

[firebird]

Dear blessedami


Good evening.

I am very very sorry for posting an incomplete and incorrect question.

I apologise for my mistake.

The question is :

An equal number of girls and boys went to a party.
The ratio of the number of girls who wore spectacles to the number of boys who wore spectacles was 11 : 3. The ratio of the number of girls who did not wear spectacles to the number of boys who did not wear spectacles was 3:5.

a) Find the ratio of the number of boys who wore spectacles to the number of boys who did not wear spectacles.

b) There were 7 time as many girls as boys who left the party. The ratio of the number of girls to the number of boys who remained at the party became 35:38. If there were 560 girls remaining at the party, how many girls left the party?

Thank you
firebird

[Dharma]

blessedami:

CJM:

hi all,


need your expertise on this...

Susan wants to buy 7 dolls which are selling at the same price. However, she needs another $11.40 in order to buy them.
She then decides to buy 3 dolls instead and and $20.20 left after that. What is the cost of each doll ?

cheers..

My DS got this answer:

7-3=4
$20.20+$11.40=$31.60
$31.60/4= $7.90

Mathsguru/Dharma- please correct him if he is wrong

To buy 4 extra dolls , she will need $31.60 ($20.20 + $11.40)
To buy 1 extra doll , she will need $31.60/4 = $7.90
Cost of 1 doll = $7.90

# Your answer DS is right, Blessedami.

[singmathstutor]

firebird:

Dear blessedami


Good evening.

I am very very sorry for posting an incomplete and incorrect question.

I apologise for my mistake.

The question is :

An equal number of girls and boys went to a party.
The ratio of the number of girls who wore spectacles to the number of boys who wore spectacles was 11 : 3. The ratio of the number of girls who did not wear spectacles to the number of boys who did not wear spectacles was 3:5.

a) Find the ratio of the number of boys who wore spectacles to the number of boys who did not wear spectacles.

b) There were 7 time as many girls as boys who left the party. The ratio of the number of girls to the number of boys who remained at the party became 35:38. If there were 560 girls remaining at the party, how many girls left the party?

Thank you
firebird

May I try??

Girls with specs: Boys with specs=11:3 --a
Girls w/o specs: Boys w/o specs=3:5 --b
All ratios are with respect to different bases, so we have to make them comparable.

For a, the difference between girls and boys with specs is 11u-3u=8u
For b, the difference between girls and boys w/o specs is 5u-3u=2u
Since there is an equal number of boys and girls at the party initially, therefore a and b should have the same difference. Notice that a's difference has a magnitude of 4 times b's difference

Therefore the relationship between all 4 types of children is as follows
Girls with specs=11u
Boys with specs=3u
Girls w/o specs=3ux4=12u
Boys w/o specs=5ux4=20u

Boys with specs:Boys w/o specs=3:20 Ans to part a

Ratio of girls:ratio of boys remaining=35:38
35u-->560
38-->608
Difference between number of boys and girls who remain=608-560=48
Girls who left:Boys who left=7:1 --c
Girls who remain:Boys who remain=35:38 --d
All ratios are with respect to different bases, so we have to make them comparable.

For c, the difference between girls and boys who left is 7u-1u=6u
For d, the difference between girls and boys who remain is 38u-35u=3u
Since there is an equal number of boys and girls at the party initially, therefore c and d should have the same difference. Notice that d's difference has a magnitude of 2 times d's difference

Therefore the relationship between all the children who left and remain is as follows
Girls who left=7u
Boys who left=1u
Girls who remain=35ux2=70u
Boys who remain=38x2=76u

76u-70u-->48
6u-->48
1u-->8
7u-->7x8=56 Ans to part b

[firebird]

Dear Singmathstutor


Good morning.

Many thanks for your detailed answer.

With best regards
Firebird

[blessedami]

Hi Firebird, No problems at all \" To err is human\"


Thanks dharma and Singmathstutor- glad that he got the answer correct, but now I can see clearly that the way you guys explain is very detailed while he is thinking from a student's point of view.

Thanks CJM- he is a P6 student.