Tutor MathsGuru: Ask me for your burning Maths questions!

[MathIzzzFun]

Herbie:

MathIzzzFun:

[quote=\"Herbie\"]Mary and ben took 49 hours to complete their sci project.

They worked separately on their own project.
If mary had worked 5 hours less an ben had worked 6 hours
More. Mary would hv put in 2 hours more than ben.
How many hous did mary put in for the sci project?

Hi

drawing a model will be easier to \"see\"..

Ben --> 1 unit
Mary --> 1 unit + 6 + 2 + 5 = 1 unit + 13
total --> 2 units + 13 = 49
1 unit --> 18
Mary --> 31 hours
Ben --> 18 hours

Thanks![/quote]u r welcome

cheers.

[Awonder]

Hi, need some help with this problem. TIA.


John is 10 years older than Tommy. In 4 years’ time, he will be twice as old as Tommy. How old is John now?

Thanks.

[ongmt]

Box A and Box B obtain the same number of apples. The number of red apples in Box A is 2/3 of that in Box B. The number of green apples in Box B is 1/4 of that in Box A, What fraction of apples in Box B are red?

[MathIzzzFun]

ongmt:

Box A and Box B obtain the same number of apples. The number of red apples in Box A is 2/3 of that in Box B. The number of green apples in Box B is 1/4 of that in Box A, What fraction of apples in Box B are red?

Hi

Difference in green apples = Difference in red apples.
Green apples, A : B --> 4u : 1u
Red apples, A : B --> 2 : 3 --> 6u : 9u
Box B, red : green --> 9u : 1u = 9 : 1

you can also look at these similar questions for the model approach
- http://www.flickr.com/photos/62167097@N02/5703951396/in/photostream
- http://www.flickr.com/photos/62167097@N02/5760364658/in/photostream

cheers.

[MathIzzzFun]

Awonder:

Hi, need some help with this problem. TIA.


John is 10 years older than Tommy. In 4 years' time, he will be twice as old as Tommy. How old is John now?

Thanks.

Hi
An important fact to note is AGE DIFFERENCE will ALWAYS remain the SAME.

In 4 years time,
John --> 2 unit
Tommy --> 1 unit
1 unit (age difference) = 10
John --> 20
Tommy --> 10
Now, John --> 20-4 = 16 years old

cheers.

[Awonder]

MathIzzzFun:

Awonder:

Hi, need some help with this problem. TIA.


John is 10 years older than Tommy. In 4 years' time, he will be twice as old as Tommy. How old is John now?

Thanks.

Hi
An important fact to note is AGE DIFFERENCE will ALWAYS remain the SAME.

In 4 years time,
John --> 2 unit
Tommy --> 1 unit
1 unit (age difference) = 10
John --> 20
Tommy --> 10
Now, John --> 20-4 = 16 years old

cheers.

Hi, thanks for yr solution. So are we assuming that Tommy is 10 years old in 4 years time? I still can't reason out myself.

[MathIzzzFun]

Awonder:

MathIzzzFun:

[quote=\"Awonder\"]Hi, need some help with this problem. TIA.


John is 10 years older than Tommy. In 4 years' time, he will be twice as old as Tommy. How old is John now?

Thanks.

Hi
An important fact to note is AGE DIFFERENCE will ALWAYS remain the SAME.

In 4 years time,
John --> 2 unit
Tommy --> 1 unit
1 unit (age difference) = 10
John --> 20
Tommy --> 10
Now, John --> 20-4 = 16 years old

cheers.

Hi, thanks for yr solution. So are we assuming that Tommy is 10 years old in 4 years time? I still can't reason out myself.[/quote]Hi

NOW,
Tommy --> 6 years old
John --> 16 years old

4 years' time,
Tommy --> 6 years + 4 years = 10 years old
John --> 16 years + 4 years = 20 years old
John's age = 2 x Tommy's age

cheers.

[Awonder]

Thanks for your explanation.

[LTQ]

This p6 maths question look simple but how can I get the right answer?


"In an enrichment class of 48 students, each student must take at least a language class or a mathematics class. 7/12 of the students choose French language and 1/4 of the students choose French language and a mathematics class. How many students choose only a mathematics class?"

Because the question ask "choose only a mathematics class", to me the answer can be from 0 to 8 students. But the answer from teacher is 20 students. Any wording trick in this question and why 20 students?

Thanks in advance.

[CoffeeCat]

LTQ:

This p6 maths question look simple but how can I get the right answer?


\"In an enrichment class of 48 students, each student must take at least a language class or a mathematics class. 7/12 of the students choose French language and 1/4 of the students choose French language and a mathematics class. How many students choose only a mathematics class?\"

Because the question ask \"choose only a mathematics class\", to me the answer can be from 0 to 8 students. But the answer from teacher is 20 students. Any wording trick in this question and why 20 students?

Thanks in advance.

Hmm actually there's something funny, The setter means language = french.
This is a \"standard\" question involving venn diagrams, so maybe you can draw it to visualise the below explanation...
The first sentence implies that any of the 48 students are either in a language (french) class ONLY, a maths class ONLY, or both classes.
(translates to : total no. of students = french only + both + math only
The venn diagram is 2 circle intersecting, 1 circle representing the total number of students in the french class and the other circle representing the total number in math class , and the intersecting region representing the number of students in both classes)

so 7/12 * 48 = 28 students are in the French class, 1/4*48 = 12 students are in both classes. Which means 28-12 = 16 students are not in maths class or in french class ONLY.

Hence the number of students in math class only is 48 - 16 -12 = 20.