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[Dharma]

Almighty:

Question no :7 : Area -EDITED


Please bear with my isoceles triangle drawing in figure 2.Assume them to be isoceles triangle .
Ten Equal isoceles triangles were cut out from a rectangular piece of paper, 30 cm long. The difference in the perimeters of figure 1 and 2 is 40 cm.Find the perimeter of each isosceles triangular piece of paper which had been cut out.
Ans :16cm
http://www.postimage.org/image.php?v=PqxS6mi

You cut 10 equal isosceles triangles from Fig ; (ie. 5 of the triangles on each side of the length of the reactangle.

Let the inclined sides of the isosceles triangle be 1 unit and the base of the triangle be 1 part

5(2 units) – 30cm = 40cm/2
10 unitrs = 50cm
1 unit = 5 cm

5parts = 30cm
1 part = 6cm

Perimeter of 1 isoceles triangle = 2unit + 1 part = 2(5cm) + 6cm = 16cm

[Maths Monster]

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[Maths Monster]

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[Almighty]

[quote="Maths Monster"]


Footnote:

This type of "Before and After" problem appears in various forms and can be solved easily. Teach the child to use a combination of model and simple algebra to form the equation. My advice is to draw all the 3 states, ie the beginning and the other two states where each gave the other some money. Then the child can start in one state and insert the ratio he/she is given, ie Ali has 5x of Lucy after Lucy gave him $8. Then the child will populate the other states using the given information. Lastly, using the other ratio, ie Lucy has 1/3 of the amount Ali has after Ali gave her $12, to form the equation which when solved will lead to the answer.

How do the child know where to put the unit "u"? The purpose of the "u" is to equate ratio/fraction/percentage. Teach the child to look for the ratio/fraction/percentage given in the question. In this question, there are two ratios, ie 5x or 3x. I used the 5x to start but either can be used. I would encourage to try using the 3x and derive the answer.

The problem many children or parents faced is when the model becomes too complex, ie too many congested boxes while trying to align them can be quite a task. This often discourage and frustrate the child. The method shown is more elegant as it doesn’t need to divide the boxes nor require alignment of the boxes. You can find good examples of using combination of Model and Algebra in this book: "The Singapore Model Method For Learning Mathematics - by the Singapore Ministry of Education". It can be found in most library or book store. Hope this helps!

It helped me a lot Maths monster.Now i picked qts like this n iam doing in yr method.I find it very simple comparitively. I am very weak in complex model drawings. Based on this method can u explaing this problem which was done in this website ina different way.I want to try in yr way…But getting stuck…pl.help
Tom had $144 more than Ali at first. After Tom spent 25% of his money and Ali spent 1/3 of his money. Tom had $122 more than Ali. How much did Tom have at first?
Thankyou very much for all other answers too.

[Almighty]

Maths Monster:

Almighty:

Question :8 - speed -EDITED

Tom, Bob and Kel;vin started running at the same point X at the same time round a circular track. Tom ran in a clockwise direction but Bob and Kelvin ran in an anti-clockwise direction. Tom took 7 minutes to complete each round. He met Bob after every 4 minutes and he met Kelvin after every 2 minutes. Each of them ran at the same uniform speed throughout.
a) What was the ratio of Toms speed to Kelvin's speed to Bob's speed?Ans:4:10:3.
b) When Tom and Bob met again at X after 21 minutes, Tom had already run 4200m. What was the distance ran by Kelvin when Tom met Bob at X after 21 minutes?
section B cannot understand the method.pl.brief.Ans:3500m

http://www.postimage.org/image.php?v=PqxSqjr

Tom ran 1 round in 7 mins. His speed is 1/7 round per min.

In 2 mins, he ran 2/7 round.
In the same time, Kelvin ran 5/7 round to meet Tom
Kelvin speed is 5/7 / 2 = 5/14 round per min.

In 4 mins, he ran 4/7 round.
In the same time, Bob ran 3/7 round to meet Tom
Bob speed is 3/7 / 4 = 3/28 round per min.

a) Ratio of speed:
Tom : Kelvin : Bob
1/7 : 5/14 : 3/28
4 : 10 : 3

b) Tom and Bob meet every 4 mins, ie in the multiply of 4.
21 / 4 = 5.25, therefore we use 6x4 = 24 mins
After 24 mins, Tom ran 24/7 rounds = 4200m
Each round = 4200 x 7/24 = 1225m

Therefore, in 24 mins, Kelvin ran 5/14 x 24 x 1225 = 10,500m

Hi mathsmonster.The answer for section b is different from the one gn in the answerkey:It states the follw:
21 min = 4200m
7min = 4200/21x7
1 round = 1400m
Kelvin completed 2.5 rounds in 7 min, so, 2.5 x 1400 = 3500m.(ANS)
I dint understand the part writted in red. Pl.explain.Sorry 2 trouble u again..

[Almighty]

Thankyou Dharma for helping me…