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maths

2008-07-16 5:11 am

4. link:http://img528.imageshack.us/img528/8664/dsc00253ra5.jpg
The dartboard shown in the figure is divided into 35 equal divisions. Landing in regions A, B, C and D gets 4, 3, 2 and 1 points respectively. A dart is thrown and hits the dartboard.
(a) Find the probability taht it lands in one of the following regions:
(i) redion A
(ii) region D
(b) Find the expected score, correct to 2 decimal places.[Assume the dart doesn't land in the boundaries.]

5. If the mean of three numbers is 13 and the mean of another five numbers is 19, find the mean of the eight numbers.

6.Given the set of data:
x/2, 4x/5, 6x/7, x/3, 7x/6
Find the value of x when the median is 8.

更新1:

2. How many km is it between two places, if a car travelling 2d km an hour takes 3 hours to finish the journet

回答 (1)

Uncle Michael

2008-07-16 7:32 am

✔ 最佳答案

4.
Among the 35 divisions:

No. of divisions of Region A = 1

No. of divisions of Region B = 2

No. of divisions of Region C = 3

No. of divisions of Region D = 8

No. of division of other region = 21

(a)
(i)
Probability that the dart lands in region A = 1/35

(ii)
Probability that the dart lands in region D = 8/35

(b)
Expected score = (1/35)x4 + (2/35)x3 + (3/35)x3 + (8/35)x3

Expected score = (4/35) + (6/35) + (9/35) + (24/35)

Expected score = 43/35

Expected score = 1.23 (to 2 decimal places)

=====
5.
Sum of the three numbers with sum 13 = 13x3

Sum of the five numbers with sum 19 = 19x5

Mean of the eight numbers = (Sum of the eight numbers) / 8

Mean of the eight numbers = (13x3 + 19x5) / 8

Mean of the eight numbers = 16.75

=====
6.
Arrange the data in ascending order :

x/3, x/2, 4x/5, 6x/7, 7x/6

The median: 4x/5 = 8

Hence, x = 10

=====
2.
Speed = 2d km/h

Time = 3 h

Distance = Speed x time

Distance = (2d km/h) x (3 h)

Distance = 6d km
=

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