If the radius of a circle is decreased by… | Answer | TuitionWave

Subject

Quantitative Aptitude

Topic

Areas & Volumes

If the radius of a circle is decreased by 50% , find the percentage decrease in its area.
Reading

ক)

75%

খ)

65%

গ)

35%

ঘ)

25%

Explanation

let original radius = r and new radius = (50/100) r = r/2 original area =

\mathrm{πr}^2

and new area =

\mathrm\pi\left(\mathrm r/2\right)^2

decrease in area =

3\mathrm{πr}^2/4

\times

\frac1{\mathrm{πr}^2}

\times

100 = 75%

The ratio between the length and the breadth of a rectangular park is 3 : If a man cycling along the boundary of the park at the speed of 12 km/hr completes one round in 8 minutes, then the area of the park (in sq. m) is:How many bricks, each measuring 25 cm x 25 cm x 6 cm, will be needed to build a wall of 8 m x 6 m x 5 cm?A large cube is formed from the material obtained by melting three smaller cubes of 3, 4 and 5 cm side. What is the ratio of the total surface areas of the smaller cubes and the large cube?A rectangular field is to be fenced on three sides leaving a side of 20 feet uncovered.If the area of the field is 680 sq.ft, how many feet of fencing will be required?A cistern of capacity 8000 litres measures externally 3 m by 6 m by 1 m and its walls are 5 cm thick. The thickness of the bottom is:The curved surface area of a cylindrical pillar is 264 m2and its volume is 924 m3. Find the ratio of its diameter to its height.A man walking at the speed of 4 kmph crosses a square field diagonally in 3 meters.The area of the field is A metallic sheet is of rectangular shape with dimensions 48 m x 36 m. From each of its corners, a square is cut off so as to make an open box. If the length of the square is 8 m, the volume of the box (in m3) is:

Find Tutors

View all Tutors