Quant Boosters  Sagar Gupta  Set 3

a + b + c = 12
total whole number solutions : 14C2 = 14 * 13/2 = 91
when a=10 : b+c =2 : 3 solutions
when a=11 : b+c =1 : 2 solutions
when a=12 : b+c = 0 : 1 solution
total 6
same when b,c = 11,12
total 6 * 3 = 18
numbers = 91 18 = 73

Q25) A number of students appear for one of the papers of the Online Cat test series. The paper consists of 100 questions. For each correct answer the candidate is awarded 1 mark and for each wrong answer 1/5th of the marks are deducted. No marks are deducted for not attempting a question. Exactly 20% of the students scored exactly 50 marks but no two attempted the same number of questions. Find the total number of students who appeared for the test?

Total students = 5x
Students who scored exactly 50 marks = x
all these x students attempted different number of questionsPossibilities for scoring 50 marks
50 correct , 0 wrong
51 correct , 5 wrong
52 correct , 10 wrong
53 correct , 15 wrong
54 correct , 20 wrong
55 correct , 25 wrong
56 correct , 30 wrong
57 correct , 35 wrong
58 correct , 40 wrongso x = 9
5x = 45

Q26) Find the maximum power of 12 in C(100,60)

100! / 60! * 40!
12 = 2^2 * 3
max power of 3 in 100! = 100/3+100/9+100/27+100/81 = 33+11+3+1 = 48
max power of 3 in 60! = 60/3 + 60/9 + 60/27 = 20 + 6 + 2 = 28
max power of 3 in 40! = 40/3 + 40/9 + 40/27 = 13 + 4 + 1 = 18
3^48 / 3^28 * 3^18 = ( 3^2 )
max power of 4 in 100! = 100/4 + 100/16 + 10/64 = 32
max power of 4 in 60! = 60/4 + 60/16 = 18
max power of 4! in 40! = 40/4 + 40/16 =12
2^32 / 2^18 * 2^12 = 2^2
so highest power is 1

Q27) A jet is flying 2400 miles from Hawaii to San Francisco. In still air, it flies at 600 mph. There is 40 mph tailwind in the same direction. Exactly how many hours after takeoff would it becomes neutral for the plane to either go to San Francisco or to return to Hawaii in the case of an emergency?
a. 1.25 hours
b. 1.5 hours
c. 1.75 hours
d. 2 hours

d / 640 = 2400  d / 560
d = 1280 miles
1280 = 640 * t
t = 2 hours

Q28) Two motorists set out at the same time to go from A to B, a distance of 100 miles. They both followed the same route and travelled at different, though uniform speeds of an integral number of miles per hour. The difference in their speeds was a prime number of miles per hour and after they had been driving for 2 hours, the distance of the slower car from A was 5 times that of the faster car from B. At what speed did the two motorists drive?

A100milesB
Sp and Sq and  Sp  Sq  = prime number
Sp * 2 = b
Sq *2 = 500  5b
10Sp + 2 Sq = 500
(42, 40) satisfies

Q29) If x/(2a+b) = y/(2b+c) = z/(2c+a) = 8 and x/2a = y/2b = z/2c = k where a + b + c not equal to 0, then k=?

x = 16a + 8b
y = 16b + 8c
z = 16c + 8a
x/2a = 8 + 4b/a
y/2b = 8 + 4c/b
z/2c = 8 + 4a/c
all are equal :
b/a = c/b = a/c : numbers are equal
8 + 4 = 12

Q30) If there are "n" students in a circular arrangement facing toward the center. It is known that their roll numbers are Integral value from 1 to "n" and they are sitting in the order of increasingroll numbers. Then what would be value of "n" if Roll number 13 is just opposite to Roll Number 29 ?

14 to 28 : 15 students
30, 31, 32 and 1 to 12 : 15 students
so total 32