Answer: B) 4 kmph Explanation: Let the distance in one direction = k kms Speed in still water = 4.5 kmph Speed of river = 1.5 Hence, speed in upstream = 4.5 - 1.5 = 3 kmph Speed in downstream = 4.5 + 1.5 = 6 kmph Time taken by Rajesh to row upwards = k/3 hrs Time taken by Rajesh to row downwards = k/6 hrs Now, required Average speed =Total distanceTotal speed = 2kk3 + k6 = 2k x 186k + 3k = 4 kmph    Therefore, the average speed of the whole journey = 4kmph.

Answer: A) Parvovirus B19 causes severe anemia because it preferentially infects erythrocyte precursors Explanation: Parvovirus B19 causes severe anemia because it preferentially infects erythrocyte precursors.   a. Parvovirus B19 binds preferentially to the erythrocyte blood group P antigen on erythroid precursor cells. Answers B, C, D are incorrect: b. after entry the single-stranded viral DNA genome is transported to the cell nucleus where the host DNA polymerase synthesizes the complimentary DNA strand. c. Parvovirus B19 infection can be diagnosed by direct detection of viral DNA not RNA. d. the fetus of a seropositive mother is protected from infection by maternal circulating antibodies.

Answer: C) C Explanation: It is explicitly given that all the 4 black balls are different, all the 3 red balls are different and all the 5 blue balls are different. Hence this is a case where all are distinct objects.   Initially let's find out the number of ways in which we can select the black balls. Note that at least 1 black ball must be included in each selection.   Hence, we can select 1 black ball from 4 black ballsor 2 black balls from 4 black balls.or 3 black balls from 4 black balls.or 4 black balls from 4 black balls.   Hence, number of ways in which we can select the black balls   = 4C1 + 4C2 + 4C3 + 4C4= 24-1 ........(A)   Now let's find out the number of ways in which we can select the red balls. Note that at least 1 red ball must be included in each selection.   Hence, we can select 1 red ball from 3 red ballsor 2 red balls from 3 red ballsor 3 red balls from 3 red balls   Hence, number of ways in which we can select the red balls= 3C1 + 3C2 + 3C3=23-1........(B)   Hence, we can select 0 blue ball from 5 blue balls (i.e, do not select any blue ball. In this case, only black and red balls will be there)or 1 blue ball from 5 blue ballsor 2 blue balls from 5 blue ballsor 3 blue balls from 5 blue ballsor 4 blue balls from 5 blue ballsor 5 blue balls from 5 blue balls.   Hence, number of ways in which we can select the blue balls= 5C0 + 5C1 + 5C2 + … + 5C5= 25..............(C)   From (A), (B) and (C), required number of ways=  2524-123-1

Answer: A) Solid carbon dioxide Explanation:   Dry ice is solid form of carbon dioxide, used as a cooling agent.   It lower temperature than that of water ice and not leave any residue.

Answer: A) 4/3 days Explanation: Let the total number of documents to be printed be 12.  The number of documents printed by P in 1 day = 4.  The number of documents printed by Q in 1 day = 3.  The number of documents printed by R in 1 day = 2.  Thus, the total number of documents that can be printed by all the machines working simultaneously in a single day = 9.   Therefore, the number of days taken to complete the whole work = 12/9 = 4/3 days.

Answer: C) 16 yrs Explanation: 12 year old Manish is three times as old as his brother Rajeev who must be 4 years old.Diff in ages = 8 years.when Rajeev will become 8 years old, Manish will be 16 yrs old and he will be twice as old as Rajeev.

Answer: A) 88572 Explanation: Given a secret is told to 3 persons in 3 minutes.And if the process continues with each person saying 3 other persons,In 30 minutes => the rocess for 10 times because each person time is 3 minutes.Required number of persons = 3 + 32 + 33 + .... + 39 + 310   Now it forms a geometric progression,   Sum to n terms is S = arn - 1r - 1   Here a = 3, r = 3  => 59048 x 3 /2   = 88572.

Answer: D) 2311 cub. cm Explanation: Given Circumference of a circular base of a cylinder = 44 cm We know that Circumference of a circle = 2πr = 44⇒r = 22π Now given the height of a cylinder h = 15 cm Volume of a cylinder V = πr2h = π22π215 = 22 x 22 x 153.14 = 2311 cm3.