Tutor MathsGuru: Ask me for your burning Maths questions!
-
Hey I noticed the flight of stairs question came back with 2 answers, 12 and 13.
@ @ @ % @ & @ @ * @ @ top
------------middle&
-------------------up 3 *
-----------down 5 %
---------------------up 8 (top)
so 12 isn’t it?
if there are 13, the middle will be in between two steps?
Or can we accept both answers as claimed by someone?
Thanks for enlightening us. -
maths6a:
Hi maths6a,Hey I noticed the flight of stairs question came back with 2 answers, 12 and 13.
@ @ @ @ @ @ @ @ @ @ @ @
Think the key here is ....
John was in the middle of a flight of steps. If he is in
the middle position, there must be an equal number of steps for John to reach the top or John to walk back down.
Total number of steps must be on ODD number ( 13 ) -
SoWoW:
How to identify whether it is a guess & check method or \"gap and differences method\" to use?[/quote]Answer is23 and not 63 because question asks for MINIMUM number of sweets.
My girl would use Guess & Check method:starlight1968sg:
[quote=\"SoWoW\"]Clara has some sweets. If she packs them in groups of 5, she will have 3 extra sweets. If she packs them in groups of 8, she will have 7 extra sweets. What is the minimum number of sweets clara has?
What is the correct method or working to show on the exam paper?
And is the answer 23 or 63? And why is that so?
thanks alot
A: 1st situation ie groups of 5 then have 3 extra
B: 2nd situation ie groups of 8 then have 9 extra
Groups: 1,2,3,4,.....
A:8,13,18,23,28
(1*5+3,2*5+3,...)
B:15,23,...
(1*8+7, 2*8+7,...)
My ans is 23. :roll:
How to identify if it's listing method of 'gap and difference' method:-
for listing questions, usually will say minimum or a range will be given, for example between 50 and 100. If in the above question, range is 50 and 100 then answer will be 63 and not 23.
For gap and difference question, the number of groups will be fixed so the question will be example,
Mr Tan gave some sweets to his pupils. If he gave each pupil 3 sweets, he would have x left and if he gave 5 sweets, then he would have y sweets left.
a) how many pupils are there?
b) how many sweets did he have?
or
If Mr Tan bought 5 books, he would have $x left and if he bought 8 books, he would be $y short, then in this case the price of each book is fixed so it's also a gap and difference question.
Questions asked can be
a) how much is each book?
b) how much money did he have?
Hope this can clarify the difference between these two types of questions.
Thanks to those who replied with how to post iamges.
Will try it out and then post the question I have with diagrams. -
http://www.postimage.org/image.php?v=TsdpVqJ
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.
Thx for the tips. With some trial and error finally got it up. Please let me know what you think of this question. Thanks. :? -
Hi all,
Can anyone help on the following qts:
1)48% of the pupils go to school by car.50% of those who donot go to school by car are girls.\t\t\t\t
25% of those who go to school by car are boys. How many percent of the total number of boys\tin the school go to school by car?\t\t
\t\t\t\t\t
\t\t\t\t\t\t
My method:\t\t\t\t\t\t
\t\t\t\t\t
\t\t\t\t\t\t
Boys :Girls\t (Car ---48%) \tBoys : Girls (Not by car -----52%\t)\t\t
12% : 36% (by car) --------\t26% :26% (Not by car)\t\t
total number of boys in the school = 12 % + 26% = 38%\t\t\t\t\t\t
total number of boys in the school go to school by car\t\t\t\t\t\t= 12% / 38% X 100
\t\t\t\t\t\t= 31 11/19%
Book answer = 12%\t\t\t\t\t\t
Can anyone clarify how can it just be 12%\t\t\t\t\t\t
2)The ratio of number of cars to the number of avns sold in a certain country\t\t\t\t\t\t
was 3:2 last year. This year. A total of 9600 more vans and cars are sold and there are twice as many vans and thrice as many cars as last year.How many cars are sold this year? \t\t
\t\t\t\t\t\t
Last year - cars sold\tThis year cars sold\t\t
C : V : Total\t\tC : V : Total\t\t
3 : 2 : 5\t\t\t 9 : 4 : 13\t\t
\t\t\t\t\t\t
\t8 units = 9600\t\t\t\t\t
\t1 unit = 1200\t\t\t\t\t
\t
So, we must find for 9 units to find the number of cars sold this year.\t
\t
ie., 9 units = 10800 carsBook method\t
6 units ( 9 - 3) ----- ? 1200 X 6\t
\t = 7200 cars
Can anyone clarify why should we do 9 - 3 ???\t
3)In a ballot school, 60% of the pupils are girls and the rest are boys.
How many percent more girls than boys are there in the ballet school?\t
\t
Girls ---60% \tBoys ----40%
\t\t\t
My method : ans : 50%\t
\t\t\t
\t20 / 40 X 100% = 50%\t\t
Work backwards:\t\t\t
50% X 40% = 20% ie , 40% + 20% = 60% \t\t\t
\t\t\t
Book method:\t\t\t
\t\t\t
Ans : 20% ie 60 % - 40%\t\t\t
\t\t\t
Work backwards:\t\t\t
20% X 40% = 8% ie., 40% + 8% = 48% not equal to 60%\t
\t\t\t
\t\t\t
My method: interpretating the question as:
How many percent more girls than boys are there in the ballet school
Book method : interpretating the question as
How many percent more girls are there than boys in the ballet school
Which is right??Can anyone please clarify on this?? :?: -
Ist of all which book are you talking about because you only mentioned ‘book’ method?
Not all books are reliable so have to be careful when using them.
Qn 1: In my opinion, in order to get the answer given by the ‘book’, the question should be phrased this way:-
What percentage of the pupils in the school are boys who go to school by car?
Qn 2: thewords used are not very clear. We could also interpret it as this year total of 13 units = 9600 cars and vans were sold? but number is not even divisible.
Qn 3: Your answer of 50% is correct. To calculate more than we have to use difference/boys x 100%. We cannot use 60 - 40 = 20 as final answer.
They are just my opinions. -
Hi again,
One more question:
http://www.postimage.org/image.php?v=TsdBLer
a) got the answer : 180Cm
For b)
My MEthod
FOr 1 glued plank ---210 cm
For 48 planks---? ie., 10080 cm
Each plank ----450 cm
?-----------10 080 cm
22.4 = 23 planks
Book method:
FOr 1 glued plank ---210 cm
for 450 cm --- 210 cm + 210 cm
No of wood needed ---- 48 /2 = 24 pieces
Am i right? If not, can anyone Please explain the book answer for (B) -
I have two questions that need guidance :-
1. Edison cycled at a speed of 10m/min while Damien cycled at a speed of 15m/min. Edison started cycling from Sleepy Town and Damien started at the same time from Happy Town. They cycled towards each other. They first met at Point Q and then continued to cycle. Upon reaching their destination, they made a U-turn and continued cycling towards each other again. This time, they met at Point R. The distance between Point Q and Point R was 324m.
(a) What was the distance between Sleepy Town and Happy Town?
(b) How long would Edison have cycled when he met Damien at Point R?
2. 2 identical tins, X and Y, were half filled with paint. Tin X contained only white paint while Tin Y contained only black paint. 1/2 of the white paint in Tin X was poured into Tin Y. After stirring the contents in Tin Y thoroughly, 1/2 of the mixed paint in Tin Y was poured into Tin X. The contents in Tin X ws mixed thoroughly and 1/2 of the mixture was then poured into Tin Y. If 7.2 litres of black paint was in the mixture in Tin X, how much white paint would there be in the mixture in Tin X?
Thank you. Cheers! -
Almighty:
Q1)Hi all,
Can anyone help on the following qts:
1)48% of the pupils go to school by car.50% of those who donot go to school by car are girls.\t\t\t\t
25% of those who go to school by car are boys. How many percent of the total number of boys\tin the school go to school by car?\t\t
\t\t\t\t\t
\t\t\t\t\t\t
My method:\t\t\t\t\t\t
\t\t\t\t\t
\t\t\t\t\t\t
Boys :Girls\t (Car ---48%) \tBoys : Girls (Not by car -----52%\t)\t\t
12% : 36% (by car) --------\t26% :26% (Not by car)\t\t
total number of boys in the school = 12 % + 26% = 38%\t\t\t\t\t\t
total number of boys in the school go to school by car\t\t\t\t\t\t= 12% / 38% X 100
\t\t\t\t\t\t= 31 11/19%
Book answer = 12%\t\t\t\t\t\t
Can anyone clarify how can it just be 12%\t\t\t\t\t\t
2)The ratio of number of cars to the number of avns sold in a certain country\t\t\t\t\t\t
was 3:2 last year. This year. A total of 9600 more vans and cars are sold and there are twice as many vans and thrice as many cars as last year.How many cars are sold this year? \t\t
\t\t\t\t\t\t
Last year - cars sold\tThis year cars sold\t\t
C : V : Total\t\tC : V : Total\t\t
3 : 2 : 5\t\t\t 9 : 4 : 13\t\t
\t\t\t\t\t\t
\t8 units = 9600\t\t\t\t\t
\t1 unit = 1200\t\t\t\t\t
\t
So, we must find for 9 units to find the number of cars sold this year.\t
\t
ie., 9 units = 10800 carsBook method\t
6 units ( 9 - 3) ----- ? 1200 X 6\t
\t = 7200 cars
Can anyone clarify why should we do 9 - 3 ???\t
3)In a ballot school, 60% of the pupils are girls and the rest are boys.
How many percent more girls than boys are there in the ballet school?\t
\t
Girls ---60% \tBoys ----40%
\t\t\t
My method : ans : 50%\t
\t\t\t
\t20 / 40 X 100% = 50%\t\t
Work backwards:\t\t\t
50% X 40% = 20% ie , 40% + 20% = 60% \t\t\t
\t\t\t
Book method:\t\t\t
\t\t\t
Ans : 20% ie 60 % - 40%\t\t\t
\t\t\t
Work backwards:\t\t\t
20% X 40% = 8% ie., 40% + 8% = 48% not equal to 60%\t
\t\t\t
\t\t\t
My method: interpretating the question as:
How many percent more girls than boys are there in the ballet school
Book method : interpretating the question as
How many percent more girls are there than boys in the ballet school
Which is right??Can anyone please clarify on this?? :?:
http://www.postimage.org/image.php?v=TsfKTo0
Q2)
Last year
Cars : 3u
Vans : 2u
This year
Cars : 9u
Vans : 4u
13u – 5u = 8u = 9600
1u = 1200
No. of cars sold this year = 9u = 9 x 1200 = 10800
Q3)
Your method is correct -
Almighty:
1/3 of Y = ¼ of XHi again,
One more question:
http://www.postimage.org/image.php?v=TsdBLer
a) got the answer : 180Cm
For b)
My MEthod
FOr 1 glued plank ---210 cm
For 48 planks---? ie., 10080 cm
Each plank ----450 cm
?-----------10 080 cm
22.4 = 23 planks
Book method:
FOr 1 glued plank ---210 cm
for 450 cm --- 210 cm + 210 cm
No of wood needed ---- 48 /2 = 24 pieces
Am i right? If not, can anyone Please explain the book answer for (B)
3u = 90cm
1u = 30cm
a)\t1 set of glued plank X + Y = 90 + 120 – 30 = 180cm
b)\tTo make 1 glued plank, Mr Tan needs 120cm length of X + 90cm length of Y
To make 1 set he needs 210cm length of plank.
1 length of plank = 4.5m = 450cm
450cm/210cm = 2.14 ( he gets 2 sets of glued plank)
So, from 1 length of plank (450cm), Mr Tan is able to make 2 pieces of glued plank.
If Mr Tan needs 48 pieces of glued plank; he needs to buy 48/2 = 24 pieces of 4.5m length plank.
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