Ash R.

asked • 01/05/15

two similar triangles have areas of 5cm square and 20 cm square respectively. if base of the smaller triangle is 4cm, find the base of the larger triangle.

IGCSE mathematics. geometry

1 Expert Answer

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Philip P. answered • 01/05/15

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The area of the larger triangle is equal to the area of the smaller one times the square of the scale factor:
 
Area of larger triangle = Area of smaller triangle * (scale factor)2
 
Hence:
 
(Area of larger triangle)/(Area of smaller triangle) = (scale factor)2
 
20/5 = (scale factor)2
 
4 = (scale factor)2
 
√4 = √(scale factor)2
 
2 = scale factor
 
Length of Base of larger triangle = Length of base of smaller triangle * scale factor
 
Can you finish it from here?
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Ash R.

thanx sir. done
plz clear this thing, that
 
Area of larger triangle = Area of smaller triangle * (scale factor)2
 
but in this question when u solve for unknown side u said;
 
Length of Base of larger triangle = Length of base of smaller triangle * scale factor
 
question is that in the first formula (scale factor)2 is used while in the 2nd one only scale factor is used. whats the reason?
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01/06/15

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