Tutor MathsGuru: Ask me for your burning Maths questions!

[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.

[trytry]

I need help with this problem.


Alice is going up an escalator.
When she takes 2 steps per second, she reaches the top in 24 steps.
When she takes 1 step per second, she reaches the top in 16 steps.
How long will she take to reach the top if she just stands on the escalator?

TIA!

[kwcllf]

??

[singmathstutor]

firebird:

Dear Singmathstutor


Good morning.

Many thanks for your detailed answer.

With best regards
Firebird

You're welcome, firebird

[singmathstutor]

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.

We gotta be detailed because we're in this profession. However, the clearer and better way is to do model drawings....which is kinda difficult here

[CoffeeCat]

trytry:

I need help with this problem.


Alice is going up an escalator.
When she takes 2 steps per second, she reaches the top in 24 steps.
When she takes 1 step per second, she reaches the top in 16 steps.
How long will she take to reach the top if she just stands on the escalator?

TIA!

May I know what's the source of this question?
Questions similar to this have appeared twice in HCI's SMOPS so far.

First notice that the first scenario is completed in a faster time.
So by the time the Alice reached the top in the first scenario, 12secs have passed, and Alice will have covered 24 steps and let the escalator covered n steps.
In the same time but in th second scenario, Alice would have covered 12 steps only (half the speed) and escalator covered n steps.
In the next 4 secs, Alice would have to cover 4 steps (16-12), and the escalator will covered 8 steps (24-16).
Because 12 secs = 3 times 4 secs, the n steps = 3*8 = 24 steps.
So the total number of steps to be covered = 24 + 24 = 48 steps.
Now for the speed of the escalator, it covered 24 steps in 12 secs (first scenario), therefore speed is 2 steps/sec. Therefore time taken if Alice stands still is 48/2 = 24 secs.

[Almighty]

Hi all,


Can anyone help to let me know whether my answer to the follwing question is right?

Yao has 2 clocks in his house; a cuckoo clock and a pendulam clock. Unfortunately,\t\t
neither is in good working condition.The cuckoo clock gains 5 seconds for every minute \t\t
it runs (which means it gets faster and faster) whilst the pendulam clock loses 5 seconds\t\t
every minute it runs (which means it gets slower and slower).Yao resets both at 6 O’clock\t\t
in the morning. When the time shown on the pendulam clock is 7.am, what time is shown on the \t\t
cuckoo clock?

(My ans : 7.10.25 am (7-hr.10 - min and 25 secs in the morning. Am I correct?)

[biscuitqueen]

Mary and Ken travelled from Town A to Town B. Mary left Town A at 0915 and took 4h to reach Town B. Ken left Town A at 1000 and took 2h 45min to reach Town B. At what time did Ken pass Mary?