How do I find a ratio of (a) the perimeters and (b) the areas of each pair of figures?
Can someone guide me through this problem? A rectangle with length 12cm and perimeter 30cm, and a rectangle with
length 10cm and perimeter 30cm.
I also need some assistance on this problem.
Concrete can be made by mixing cement, sand, and gravel in a 3:6:8 ratio.
How much gravel is needed to make 850cm2 of concrete?
1 Answer | Add Yours
1) Given Length of First Rectangle (L1) = 12 cm and Length of Second Rectangle L2=1O cm
Perimeter of First Rectangle (P1) = 30 cm , Perimeter of Second Rectangle(P2)=30 cm
Let B1 and B2 be the breadths of the two rectangles
We know that Perimeter of Rectangle = Sum of all sides
= 2( Length + Breadth)
Therefore P1 = 2( L1+B1)
30= 2(12+B1) = 24+2B1
B1= 3 cm
30=2(10+B2) = 20+2B2
Now Area of Rectangle = Length x Breadth
Therefore Area of First Rectangle (A1) = L1 X B1= 12 X 3 = 36 sq.cm
Area of Second Rectangle (A2) = L2 X B2 = 10 X 5 = 50 sq.cm
Ratio of Perimeter = P1/P2 = 30/30 = 1
Ratio of Area = A1/A2 = 36/50 =18/25 = 0.72
2) It is given that the ratio of Cement : Sand : Gravel = 3:6:8
Sum of the ratios = 3+6+8 = 17
Therefore Gravel needed to make 850 sq.cm concrete = (8/17) x 850
= 8 x 50
Gravel needed = 400 sq.cm.
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