8th Grade OST Math FREE Sample Practice Questions

8- A
Percent of cities in the type of pollution A:
\(\frac{6}{10} × 100=60\%\)
Percent of cities in the type of pollution C:
\(\frac{4}{10} × 100 = 40\%\)
Percent of cities in the type of pollution E:
\(\frac{9}{10}× 100 = 90\%\)

9- A
Let the number of cities be added to the type of pollution B be \(x\). Then:
\(\frac{x + 3}{8}=0.625→x+3=8×0.625→x+3=5→x=2\)

10- A
AB\(=12\) And AC\(=5\)
BC\(=\sqrt{(12^2+5^2 )} = \sqrt{(144+25)} = \sqrt{169}=13\)
Perimeter \(=5+12+13=30\)
Area \(=\frac{5×12}{2}=5×6=30\)
In this case, the ratio of the perimeter of the triangle to its area is:
\(\frac{30}{30}= 1\)
If the sides AB and AC become twice longer, then:
AB\(=24\) And AC\(=10\)
BC\(=\sqrt{(24^2+10^2 )} = \sqrt{(576+100)} = \sqrt{676} = 26\)
Perimeter \(=26+24+10=60\)
Area \(=\frac{10×24}{2}=10×12=120\)
In this case the ratio of the perimeter of the triangle to its area is:
\(\frac{60}{120}=\frac{1}{2}\)

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