Ratio of areas

Geometry Level 2

Given the figure above, find the ratio of the area of the shaded region to the area of the unshaded region. Give your answer as a decimal number to two decimal places.


The answer is 0.16.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Hassan Abdulla
Feb 7, 2018

Area of x = Area of rectangle - Area of half circle x = ( r × 2 r ) ( π 2 r 2 ) = r 2 ( 2 π 2 ) Area of y = Area of equilateral triangle 3 × ( 1 6 Area of circle ) //sector with angle 60° y = 3 4 ( 2 r ) 2 π 2 r 2 = r 2 ( 3 π 2 ) Area of shaded = 8 x + 10 y = r 2 ( 16 + 10 3 9 π ) Area of unshaded = 10 × A r e a o f c i r c l e = r 2 ( 10 π ) the ratio = r 2 ( 16 + 10 3 9 π ) r 2 ( 10 π ) = 16 + 10 3 9 π 10 π 0.16 \text{Area of x = Area of rectangle - Area of half circle}\\ x=(r\times 2r)-(\frac { \pi }{ 2 } r^{ 2 })=r^{ 2 }(2-\frac { \pi }{ 2 } )\\ \text{Area of y = Area of equilateral triangle} - 3\times \color{#3D99F6} (\frac { 1 }{ 6 } \text{Area of circle}) \text{//sector with angle 60°}\\ y=\frac { \sqrt { 3 } }{ 4 } (2r)^{ 2 }-\frac { \pi }{ 2 } r^{ 2 }=r^{ 2 }(\sqrt { 3 } -\frac { \pi }{ 2 } )\\ \text {Area of shaded }= 8x+10y=r^{ 2 }(16+10\sqrt { 3 } -9\pi )\\ \text {Area of unshaded} = 10\times Area of circle=r^{ 2 }(10\pi )\\ \\ \text {the ratio} =\frac { r^{ 2 }(16+10\sqrt { 3 } -9\pi ) }{ r^{ 2 }(10\pi ) } =\frac { 16+10\sqrt { 3 } -9\pi }{ 10\pi } \approx 0.16

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...