SSC CGL 202011)A circular disc of area \(0.64\pi\space m^2\) rolls down a length of 1.408 km. The number of revolutions it makes is: (Take \(\pi ={22\over7}\))
280
Area = \(\pi r^2\);
\(\pi r^2= 0.64\pi\space m^2\);
r = 0.8 m;
Circumference of disc = \(2 \pi r = 2 \times (22/7) \times 0.8 = 5.02\) ;
Length = 1.408 km = 1408 m;
The number of revolutions = 1408/5.02 = 280
SSC CGL 202012)A metallic sphere of diameter 40 cm is melted into smaller spheres of radius 0.5 cm each. How many such small balls can be made?
64,000
Number of smaller balls = \({Volume \space of\space bigger \space ball\over Volume\space of \space a\space smaller\space ball}\) = \({{4\over3}\pi R^3\over {4\over3}\pi r^3}=({20\over0.5})^3= 64000\)
SSC CGL 202013)The perimeter of a square is 64 cm. Its area will be:
256 \(cm^2\)
Perimeter of square = 64 cm ; ⇒ 4 x Side = 64; ⇒ Side = 16 cm; Area of square = \((Side)^2=(16)^2 = 256 \space cm^2\)
SSC CGL 202014)The diagonal of a square A is (a + b) units. What is the area (in square units) of the square drawn on the diagonal of square B whose area is twice the area of A?
\(2(a+b)^2\)
Area of square A = \( \frac{(diagonal)^2}{2} = \frac{(a + b)^2}{2}\) ;
Area of square B = \(2 \times area \space of \space square A = 2\times \frac{(a + b)^2}{2} = (a + b)^2\) ;
Side of B = a + b ;
Diagonal of B = \(\sqrt{2} side = \sqrt{2}(a+b)\) ;
Area (in square units) of the square drawn on the diagonal of square B = \((side)^2 = (\sqrt{2}(a+b))^2 = 2(a + b)^2\)