Question

The figure shows a circular dartboard. Its surface consists of two concentric circles of radii 12 cm and 2 cm respectively.
(a) Find the area of the shaded region on the dartboard.
>>>140π cm2<<<
(b) Two darts are thrown and hit the dartboard. Find the probability that
(i) both darts hit the shaded region;
(ii) only one dart hits the shaded region.

@ganeshie8 @hba

Answer 1

total area of dartboard = 144 pi ?

Answer 2

if so,
for part b)
(i) both darts hit the shaded region;
(140pi/144pi) * (140pi/144pi)

Answer 3

yes

Answer 4

sorry, the first area is correct

total area = pi*12^2 = 144pi

so,
for part b)
(i) both darts hit the shaded region;
(140pi/144pi) * (140pi/144pi)

(140/144)^2

Answer 5

whats the answer ?

Answer 6

oh wait. the first one is correct... [(140pi)/(144pi)] ^(2)=1225/1296
sorry. i press the calculator wrongly....

Answer 7

good :)

Answer 8

let me delete the 196 thingy

Answer 9

why part b i get 5526.978465...?! IMPOSSIBLE -.-

Answer 10

(ii) only one dart hits the shaded region.
(140pi/144pi) * (4pi/144pi) + (140pi/144pi) * (4pi/144pi)

2[(140/144) * (4/144)]

35/648

Answer 11

see if that makes sense

Answer 12

oh, so complicated...
ohh i forgot the plus -.-"
thank you very much. the answer is also correct. Great job ganeshie8 :) !

Answer 13

np :)
we have used below :

probability for only one dart hits the shaded region =
(probability for first dart in shaded region AND second dart in clear region) + (probability for first dart in clear region AND second dart in shaded region)

Answer 14

ohh i have really learnt this but i forgot :P thanks

Answer 15

happens lol... wlc :)