Tutor MathsGuru: Ask me for your burning Maths questions!

[Superbugs]

Pls help with this question too with other method other than guess and check:


Farmer Tan has ducsk and cows on his farm. The total number of ducks and cows is between 20 and 40. The ratio of the total no. of duck’s legs to the total no. of cow’s legs is 5:9. What is the total no. of ducks and cows on the farm?

Duck=> 2 legs
Cow=> 4 legs
Ratio of duck’s legs to cow’s leg
5:9
Since cow has 4 legs, I multiply the duck ratio by 2 to be on par with the cow legs, I get 10:9 => 19
Then guess and check method:
20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40
Since only 38 can be divisible by 19, the ans is 38.
Is this method correct?

Any other method?

[Dharma]

Total No. of Ducks = D

Total No. of Cows = C
Total no. of legs = 2D + 4C

Ratio of the no. of legs of ducks : no. of legs of cows = 2D : 4C = 5 : 9
18D = 20C
D : C = 20 : 18

Total no. of ducks and cows = 20 + 18 = 38

[MathIzzzFun]

Superbugs:

Hi there, someone pls help me with the following questions:


Mdm Lek had 57 apples and oranges altogether. There were 3 fewer oranges than apples. Sh egave away half as many oranges as apples and was left with twice as many oranges as apples. How many apples did she give away?

I can only do up to here:
2U+3 => 57
1U=>27
Oranges =>27
Apples => 27+3 => 30

Hi

Hope this helps :lol:

http://www.flickr.com/photos/62167097@N02/5705956596/in/photostream

cheers.

[bleeze]

Hi, someone pls help me with the following question:


There were 1260 boys and girls in an amusement park. When 5/8 of the girls and 7/13 of the boys left the amusement park, the number of boys and the number of girls remaining in the park is the same. How many more girls than boys were there in the amusement park at first?

Ans: 140

Thanks

[Superbugs]

Dharma:

Total No. of Ducks = D

Total No. of Cows = C
Total no. of legs = 2D + 4C

Ratio of the no. of legs of ducks : no. of legs of cows = 2D : 4C = 5 : 9
18D = 20C
D : C = 20 : 18

Total no. of ducks and cows = 20 + 18 = 38

How did you derive at 18D:20C? You mean cross multiply 2D with 9 and 4C with 5? If yes, why?

[Superbugs]

MathIzzzFun:

Superbugs:

Hi there, someone pls help me with the following questions:


Mdm Lek had 57 apples and oranges altogether. There were 3 fewer oranges than apples. Sh egave away half as many oranges as apples and was left with twice as many oranges as apples. How many apples did she give away?

I can only do up to here:
2U+3 => 57
1U=>27
Oranges =>27
Apples => 27+3 => 30

Hi

Hope this helps :lol:

http://www.flickr.com/photos/62167097@N02/5705956596/in/photostream

cheers.

Wow impressive. I got it. Tks a lot.
Can anyone help with my earlier two questions pls. Tks

[Superbugs]

Hi I have another question, kindly assist:


Four containers A,B,C & D contained a total of 230 buttons at first. Then the no. of buttons in A was increased by 55, the no. in B was decreased by 15, the no. in C was doubled and the no. in D was halved. As a result, the no. of buttons in each container was the same. Find the no. of buttons in D at first?

If the no. of buttons in each container was the same at the end, why can’t I use 230/4=57.5 (not a whole no???)

I used the model method but not sure if this is correct understanding:

At first
A=>2U-55
B=>2U+15
C=>U
D=>4U

9U=230-15+55
9U=270
1U=30
4U=120

[CoffeeCat]

bleeze:

Hi, someone pls help me with the following question:


There were 1260 boys and girls in an amusement park. When 5/8 of the girls and 7/13 of the boys left the amusement park, the number of boys and the number of girls remaining in the park is the same. How many more girls than boys were there in the amusement park at first?

Ans: 140

Thanks

There is something wrong with this question. Working backwards, there are 700 girls and 560 boys at first. But 700 is not divisible by 8.
But otherwise this is my working for such qns...
This is an equal concept question, because
3/8 of the girls = 6/13 of the boys
What we want is the ratio of girls to boys, there are different methods, mine is to make the numerator equal.
6/16 of girls = 6/13 of boys.
So there are 16 units of girls and 13 units of boys.
1 unit ->1260/29 = ???

[CoffeeCat]

Superbugs:

Hi I have another question, kindly assist:


Four containers A,B,C & D contained a total of 230 buttons at first. Then the no. of buttons in A was increased by 55, the no. in B was decreased by 15, the no. in C was doubled and the no. in D was halved. As a result, the no. of buttons in each container was the same. Find the no. of buttons in D at first?

If the no. of buttons in each container was the same at the end, why can't I use 230/4=57.5 (not a whole no???)

I used the model method but not sure if this is correct understanding:

At first
A=>2U-55
B=>2U+15
C=>U
D=>4U

9U=230-15+55
9U=270
1U=30
4U=120

Your model method is correct =).
You cant use 230/4 initially after the total number of buttons after the changes is not guaranteed to be still 230.

[CoffeeCat]

Superbugs:

Hi there, appreciate it that someone can assist me on the following questions:


Q1) There are 8 stacks of chairs and 12 chairs in each stack. Each chair is equally spaced apart to form the perimeter of a rectangle. If the no. of chairs placed along its length is thrice the no. of chairs placed along its breadth, how many chairs are placed equally along one of the length of the rectangle.

12x9 = 108
108-4 (4 corners) = 104
108/8 = 13
13x3=39
39+2 (2 corners) = 41

But the answer is 42 and instead of minusing the 4 corners, they add the 4 corners
108+4=112
112/8=42
Why is that so?

Q2) J bought some strawberries and wanted to put them in boxes. If she put 4 strawberries into each box, there would be 3 strawberries left. If she put 6 strawberries into eah box, she would have 5 strawberries left.

If the no. of strawberries was between 100 and 150, how many strawberries did J buy?

I used the common multiple method but got many answers:

Common Multiple of 4, starting with 100 plus 3 excess:
103, 107, 111, 114, 119, 123, 127, 131, 135 etc

Common Multiple of 6, starting with 102 plus 5 excess:
107, 113, 119, 125, 131, 137

Why the answer is not 107 or 119 but 131? If this is not the correct method to apply, any other method?

Qns 1)
\"If the no. of chairs placed along its length is thrice the no. of chairs placed along its breadth\".
The 4 corners....the 4 chairs are only counted once. So you have to add 4 so that you really get the total no. of chairs for length + breadth. If you minus the 4, then the above sentence is no longer true.
Qns 2)
Maybe there is a typo with the question. Your method is correct. Although the fastest direct method is to notice that any number which is 1 less than a multiple of 12 will satisfies the 2 conditions.
(let the ans be x. Notice x+1 will be a common multiple of 4 and 6, implying x+1 must be a multiple of 12)