extra ex 12 answer.pdf

Extra Revision Exercise 12327Extra Revision Exercise 12Multiple Choice Questions=NK A die is thrown. The probability of not getting aprime number is^K16 ._K12 .`K23 .aK56 .B=QK Two coins are tossed at random. Find theprobability of getting a head and a tail.^K14_K12`K34aK 1B=OK A card is drawn at random from a pack of playing =RK A letter is chosen at random from the wordscards. The probability of getting a heart isafter and fact respectively. The probability1^K52 .that the two letters are the same is1^K1_K13 .20 .1_K4`K13 .10 .31aK4 .D `K20 .1=PK A bag contains 8 white balls, 4 black balls and 8aK5 .Cred balls. A ball is drawn at random from the bag.=SK Mrs. Chan has two sons. Now she is pregnant.The probability that the ball is black isThe probability that the third child is a girl is1^K20 .^K 0.1_K8 .1_K3 .1`K5 .1`K2 .C1aK4 . C aK 1.

328 Chapter 12 Simple Idea of Probability=TK Form 3A has 40 students in which 28 are boys. Astudent is chosen at random to be the class monitor.The probability that the class monitor is a girl is1^K40 .3_K10 .7`K10 .1aK12 .BRefer to the table below and answer questions U=to V.A nurse has measured the body temperatures of 100patients. The results are recorded as follows:Body temperature (°C)Frequency37.0 037.5 638.0 1438.5 4239.0 2239.5 1040.0 540.5 1UK The experimental probability that the bodytemperature of a patient is below 39.25°C is^K110 ._K2150 .`K12 .aK2125 . DVK The experimental probability that the bodytemperature of a patient is above 40.25°C is^K 0._K1100 .`K350 .BaK 1.NMK A person has three keys. One of them can open theentrance door and the others can open the roomdoors. If one of the keys is chosen to open theentrance door and one of the remaining two keysis chosen to open a certain room door, find theprobability that the two doors can be opened.^K18 ._K16 .`K13 .aK12 .CNNK There are 10 coupons. Two of them cost $100while the others cost $10. A coupon is drawn atrandom, find the expectation of the cost of thecoupon drawn.^K $10._K $18.`K $20.aK $28.D

Extra Revision Exercise 12329Level OneNOK A bag contains 20 coins in which 6 coins are $1. A coin is drawn at random from the bag. What is the probability3that the coin is a $1 coin?10NPK A bag contains 9 apples, 6 oranges and 5 peaches. If a fruit is drawn at random from the bag, find the probability7that the fruit is not an orange.101NQK Mr. Chan has one son and one daughter. What is the probability that the daughter is older than the son?2NRK A card is drawn at random from a pack of 52 playing cards. Find the probability that this card is a heart or a7card marked A .1311NSK Two dice are thrown. Find the probability that at least one of the numbers is 6.36 411NTK A letter is chosen at random from the word MATHEMATICS . Find the probability that the letter is a vowel.NUK A bag contains 15 balls which are red or white. A ball is drawn at random from the bag. If the probability ofgetting a red ball is 2 , how many red balls are there in the bag? 65NVK A letter is chosen at random from the word CALCULATOR . Find the probabilities that the letter is1E~F A .5 2EÄF a vowel. 5 3EÅF C or T.10OMK A boy has tossed a coin three times, and three heads are got. If the boy is going to toss the coin once more,1what is the probability of getting a head?2ONK A bag contains two $1 stamps, six $0.5 stamps and ten $0.1 stamps. If a stamp is drawn at random from thebag, find the expectation of the value of the stamp. $ 1 3OOK Two dice are thrown. Find the probabilities with the following outcomes by using a table.2E~F The difference of the two numbers is 2.91EÄF The difference of the two numbers is greater than 2.3OPK Mrs. Lee has three children. Suppose that the probabilities of having a boy and a girl are the same. Find theprobabilities with the following outcomes by using a tree diagram.3E~F Mrs. Lee has two daughters and one son.EÄF Mrs. Lee has at least one son. 788OQK There are three blood donators. Two of them have blood type O andthe other has blood type A. Now a person is chosen at random fromthem. After one year, a person is chosen at random from them again.4Find the probability that both of them have blood type O.9

330 Chapter 12 Simple Idea of ProbabilityORK A company has five staff in which three are female and two are male. There are one female and one male staffwhose first names are Ting. Given that one female and one male staff will be promoted this year, find theprobabilities that1E~F the first names of the two staff promoted are Ting.6EÄF the first names of the two staff promoted are not Ting.EÅF the first name of one of the staff promoted is Ting. 1213OSK Some balls are marked with the numbers from 0 to 39 one by one. A ball is chosen at random from them.Find the probabilities that7E~F the number is a multiple of 5.403EÄF the number is a prime number.10Level TwoOTK A box contains four cards marked 1 , 2 , 3 and 4 . A card is drawn at random from the box. Afterrecording its number, the card is replaced into the box. The second card is then drawn again. Find the probabilitiesthat1E~F both numbers are odd number.41EÄF the sum of the two numbers is 5.4EÅF the two numbers are the same. 14OUK In the figure, there are two wooden boards (A and B) that have beenmarked with numbers. John and Sam hit the wooden boards A andB respectively with arrows. Suppose that the probability of hittingeach number is the same. Find the probability that1E~F both numbers are 1.12 1EÄF both numbers are the same.41EÅF the sum of the two numbers is 5.41EÇF both numbers are odd numbers.3OVK A boutique has bought some new clothes of five different styles A, B, C, D and E. Each style has three clothesof different sizes (large, medium and small). If a new clothes is chosen at random, find the probabilities that1E~F the style is A or B, and the size is large.58EÄF the size is medium or small, and the style is not C.151EÅF the size is small.3EÇF the style is E. 215PMK A bag contains 8 cards of different colours in which 3 are red, 2 are blue, 2 are yellow and 1 is green. Red,blue, yellow and green cards represent scores of 1, 2, 2 and 3 respectively. A card is drawn at random from thebox. Find the expectation of the score. 1 3 4

Extra Revision Exercise 12331Level ThreePNK Destinations X and Y are joined by three paths A, B and C. Sammitravels from X to Y, while Andy travels from Y to X. Find theprobabilities that1E~F both of them travel by path A.91EÄF both of them travel by the same path.3 1EÅF Sammi travels by path A, while Andy travels by path B.9POK A bag contains four coins of $10, $5, $2 and $1. Two coins are drawn at random from the bag. Find theprobabilities of getting1E~F a total value of $3. 61EÄF a total value less than $10.2 2EÅF a total value more than $6. 3PPK In the 100 years from 1898 to 1997, the numbers of times that the first day of the lunar year appeared in eachday of a week are shown as follows.Day Sunday Monday Tuesday Wednesday Thursday Friday SaturdayFrequency 12 12 19 12 15 13 17One of the 100 years is chosen at random. Find the probabilities that in this year3E~F the first day of the lunar year was on Monday.25 3EÄF the fifteenth day of the lunar year was on Sunday.25 3EÅF the thirtieth day of the lunar year was on Thursday.25PQK In a class, the ratio of the number of boys to that of girls is 3 : 2. 20% of boys and 30% of girls have failedthe Mathematics test. Now a student is chosen at random from the class. Find the probabilities thatE~F the student is a girl who has failed the Mathematics test. 0.12EÄF the student has passed the Mathematics test. 0.76PRK The figure shows a circular target board with radius 12 cm. If thearrow hits the shaded region, 5 marks will be given. If the arrow hitsthe striped region, 3 marks will be given. If the arrow hits the whiteregion, only 1 mark will be given . Find the expectation of the totalmarks of 3 arrows that hit the target board. 6 1 marks312 cm4 cm4 cm